Theoretical Medicine and Bioethics

, Volume 35, Issue 4, pp 289–310 | Cite as

A Thomistic appraisal of human enhancement technologies



Debate concerning human enhancement often revolves around the question of whether there is a common “nature” that all human beings share and which is unwarrantedly violated by enhancing one’s capabilities beyond the “species-typical” norm. I explicate Thomas Aquinas’s influential theory of human nature, noting certain key traits commonly shared among human beings that define each as a “person” who possesses inviolable moral status. Understanding the specific qualities that define the nature of human persons, which includes self-conscious awareness, capacity for intellective thought, and volitional autonomy, informs the ethical assessment of various forms of enhancement. Some forms of cognitive and physical enhancement may be desirable from the perspective of what constitutes the “flourishing” of human persons in our fundamental nature; while other forms of enhancement, such as emotive or so-called “moral” enhancement, run the risk of detracting from human flourishing when evaluated from the virtue-theoretic perspective Aquinas promotes.


Enhancement Personhood Human nature Transhumanism Virtue Thomas Aquinas 


Debate concerning the enhancement of human capacities through genetic, pharmacological, or technological means often revolves around the question of whether there is a common “nature” that all human beings share and which is unwarrantedly violated by enhancing a human being’s capabilities beyond the normal levels defined by this shared nature. In this paper, I will explicate Thomas Aquinas’s view of human nature, noting certain key traits commonly shared among human beings that define each as a “person” who possesses inviolable moral status. While I have elected to focus upon Aquinas’s theory of human nature given the degree of its influence, particularly among bioconservatives, I will note how other historical and contemporary theories of human nature cohere with the Thomistic account.

Understanding the specific qualities that define the nature of human persons, which include self-conscious awareness, capacity for intellective thought, and volitional autonomy, informs the ethical assessment of various forms of human enhancement. Some forms of enhancement—assuming they are demonstrably safe and efficacious—for certain types of capacities may be not only morally permissible, but even desirable from the perspective of what constitutes the “flourishing” of human persons in our fundamental nature as rational animals—for example, enhancing one’s immune system or memory capacity. Other forms of enhancement, however, run the risk of detracting from human flourishing or altering one’s nature in ways that would lead to complicated social relationships with other human persons or diminishing one’s moral agency, with the result that such forms of enhancement ought not to be pursued—for example, attempts to enhance one’s emotive responses. Finally, I will evaluate attempts to “morally enhance” human beings from the virtue-theoretic perspective Aquinas promotes.


A few caveats are in order before I proceed so as to define the scope of the present analysis. Each of the issues raised by these caveats is only briefly addressed here but merits its own detailed analysis, which I hope to provide in a longer treatment of the ethics of human enhancement in another article. First, I will not enter into the ongoing debate over whether there is a valid distinction between treatment versus enhancement [1, 2]. Rather, I will assume that there are some clear-cut cases of human enhancement beyond the “species-typical” norm [3, pp. 149–155]. The question at hand is whether such forms of human enhancement are morally permissible or problematic.

Second, I will not be discussing any of the practical issues related to developing such enhancements, but will presume that the enhancements under discussion have been proven—at present or at some future time—to be safe and efficacious. If any proposed enhancements prove not to be safe and efficacious, then they would be morally impermissible on even the most permissive ethical analysis. As Norman Daniels notes, however, the experimental route to demonstrating that some forms of human enhancement are safe and efficacious may be too disproportionate in terms of the risk/benefit ratio such that we cannot ethically get there from here [4, p. 38]. If Daniels is correct, then this entire discussion is moot—at least for those forms of enhancement the long-term effects of which are not in principle determinable or even reasonably predictable. Nevertheless, reasonable predictions may be made for some forms of enhancement such that they may proceed ceteris paribus on the expectation that the risk/benefit ratio—once verified empirically—will result in their favor.

Third, I will be limiting my analysis to whether certain forms of human enhancement are permissible or problematic on the basis of whether they alter human nature in ways that do not contribute to but, rather, inhibit the individual or collective flourishing of human beings. Enhancement in general, or a particular form of enhancement that may be judged permissible according to the present analysis, may be evaluated as in principle morally impermissible due to other factors—for example, it may erode our appreciation of the inherent “giftedness” of nature while betraying a Promethean drive towards “mastery” over nature [5].1

Fourth, I rule out as morally impermissible any means toward achieving human enhancement that involves either the destruction or eugenic selection of human embryos or fetuses. Rather, all approvable means of enhancement must respect the inviolable life and bodily integrity of the individual being enhanced. In other words, permissible enhancements involve making this person better, not selecting one person over another as genetically superior.

Finally, I will not discuss the important issue of whether human societies, or the “global village” as a whole, may become socially disrupted by virtue of an increase in socioeconomic disparity if enhancements are available for only a select few who enjoy wealth or high social standing. Suffice it to say, given the Thomistic model of human flourishing I will elucidate, such severe social disruption would likely render such enhancements impermissible, or at least problematic in the absence of alternative social support mechanisms for the unenhanced to ameliorate the effects of such increased socioeconomic bifurcation.2 In sum, then, the focus of this analysis is whether particular forms of human enhancement, demonstrated to be safe and efficacious, and which are readily available to all who desire them, are in principle morally permissible or problematic with respect to a Thomistic concept of human nature and flourishing.

Human enhancement

There are myriad forms of, means by, and ends for which human capabilities may be enhanced. Hence, it is difficult to justify a blanket approval or disapproval of all forms of enhancement.3 Rather, each particular form of enhancement, or means by which it is achieved, should be morally evaluated on its own merits:

Whether we should employ a particular enhancement depends on the reasons for and against that particular enhancement. Creating superimmunity to all known biological and viral insults is very different from practicing sports doping; choosing the personality traits of our offspring through genetic selection is very different from taking a pill that temporarily boosts our ability to concentrate. On this line of reasoning, it is time to take a further step, from asking “Should we do it?” to analyzing the “it” and asking a number of much more specific questions about concrete actions and policy options related to particular enhancement issues within a given sociopolitical-cultural context. The result of this will not be a yes or no to enhancement in general, but a more contextualized and particularized set of ideas and recommendations for how individuals, organizations, and states should move forward in an enhancement era. [11, p. 19]

The basic forms of human enhancement I will discuss are cognitive, physical, emotive, and moral. With respect to specific means by which such forms of enhancement may be achieved, I do not draw any a priori moral distinctions between genetic, technological, or pharmacological approaches; although, some means may have more or less effect, for good or ill, on the ontology of human nature as will be elucidated below.4 Finally, I contend that the only morally laudable end for which enhancements may be pursued is the individual or collective flourishing of human persons, understood in the Thomistic sense. Enhancements for purely hedonistic ends or as a mere exercise of autonomy—understood in a liberal, individualist sense—are not commensurate with the Thomistic view adopted for this analysis. The Thomistic concept of autonomy is similar to the Kantian concept insofar as the unbridled exercise of an individual’s will without any internal or external constraints is not the goal; rather, it is the will’s capacity to self-legislate—that is, to govern oneself in accordance with the rationally understood moral law [13]. Thus, an agent’s exercise of her autonomy should lead to both individual and collective flourishing. This communitarian perspective is at odds with a libertarian concept of an agent’s autonomy, which does not necessarily lead to one’s own flourishing—if an agent wills to engage in self-destructive behavior—nor contribute to the common good.5

General reasons in favor of enhancement

Those who generally favor human enhancement—often self-identified as “transhumanists”—typically offer a three-pronged argument to make their case [16, 17, 18, 19]. They first highlight all the potential benefits that enhancement may yield in terms of physical, cognitive, social, and moral improvement over our current, naturally given, condition.

Second, they presume in favor of the liberal conception of individual autonomy, such that the burden of demonstration is on those who would restrict the freedom of individuals who wish to enhance themselves or their children. The contrast between a liberal and a Thomistic conception of autonomy—as described above—is premised upon the question of whether there is an objective standard for human flourishing, such that certain forms of enhancement would be good or bad for human beings generally, or whether what counts as “good” for a particular person can only be defined subjectively by her and thus she should have the freedom to pursue her own conception of what constitutes a flourishing life [20; 21, pp. 5–6]. Transhumanists thus advocate a right to “morphological freedom,” defined as “the right to modify and enhance one’s body, cognition, and emotions” [22, 23]. Such theorists recognize reasonable limits to the exercise of such autonomy insofar as they foresee legitimate enhancements as often contributing to the amelioration of social issues and not merely the exercise of individual preferences; nevertheless, they advocate the freedom to satisfy individual preferences so long as wider social harms do not thereby result. The Thomistic view of autonomy differs insofar as such “wider social harms” are objectively, and not merely conventionally, defined; furthermore, individuals may be legitimately protected from objectively harming themselves through the satisfaction of irrational preferences, even if no third-party harms are implicated.

Third—and most relevant to the present discussion—they contend that human nature, as given, is not fixed but malleable and that the application of human intelligence is likely to result in superior alterations to the human form than the “blind” process of continued biological evolution:

Transhumanists view human nature as a work-in-progress, a half-baked beginning that we can learn to remold in desirable ways. Current humanity need not be the endpoint of evolution. Transhumanists hope that by responsible use of science, technology, and other rational means we shall eventually manage to become post-human, beings with vastly greater capacities than present human beings have. [17, p. 493]

Representative of this viewpoint is the opening chapter of the collection, Enhancing Human Capacities [12], the authors of which reject as “ideological” any understanding of enhancement that rests upon a metaphysical concept of human nature and adopt a “welfarist” definition, in which an enhancement is “any change in the biology or psychology of a person which increases the chances of leading a good life in the relevant set of circumstances” [24, p. 7]. Of course, this definition, consequentialist in tone, leaves open to debate what may be considered a “good life” for human beings. Following John Rawls [25, pp. 78–81] and others [26, pp. 167–170], the authors adopt a notion of “all-purpose goods,” which may subserve human flourishing in a wide variety of lifestyle and career choices [24, p. 11]. The list of such goods includes various cognitive abilities. Thus, they conclude that, as safe and efficacious cognitive enhancement technology becomes available and affordable, “parents will have a duty to enhance their children” [24, p. 16]. Cognitive enhancements would be on an ethical par with enhancing the immune system of one’s child through vaccinations.

It is important to note that the goal of transhumanists and their fellow-travellers is not perfection, but rather a continued increase of human capabilities asymptotically. Max More describes the overarching transhumanist goal as “perpetual progress,” not “seeking a state of perfection” [6, p. 5]. It remains the case that an enhanced human being will be subject to all kinds of contingencies that may forever be insurmountable. Hence, while an enhanced human being may be tempted towards less humility or gratitude for the gifts—engineered or naturally-endowed—that she possesses, a reasonable appreciation of just how much remains completely outside of human control, no matter how great one’s capabilities may be, should inspire the continued cultivation of the virtues of humility and gratitude in the face of somatic vulnerability and the changing winds of fortune.6

Objections to enhancement based on “human nature”

Although there are various objections either to human enhancement in general or to particular forms of enhancement, I will focus on two related foundational principled objections: (1) enhancements may alter human nature, which is sacrosanct; (2) alteration or destruction of human nature will negatively impact our capacity to understand and pursue what is objectively good in terms of human flourishing.7 Understanding and replying, either affirmatively or negatively, to these objections requires the development of a defensible objective definition of “human nature” and establishing its inherent normative value.

Arthur Caplan, however, raises the basic challenge to those who object to human enhancement on the basis that it violates our shared “nature” in objectionable ways:

Is there a “nature” that is common to all humans, both those that exist now and those that have existed in the past? … one can concede that we have been shaped by a causally powerful set of genetic influences and selection forces and still remain skeptical as to whether these have produced a single “nature” that all members of humanity possess. What exactly is the single trait or fixed, determinate set of traits that defines the nature of who humans are and have been throughout our entire existence as a species on this planet? … Without a demonstration of a “nature” there is no basis for the claim that change, improvement, and betterment always represent grave threats to our essential humanity. [33, p. 202]

Despite all that we have learned about the biological and sociological evolutionary development of human beings, metaphysical analyses from both historical and contemporary philosophers have consistently—if not uncontroversially—defended a fairly coherent list of universal human qualities that emerge through such development. In the classical period, both Plato and Aristotle defined the essence of humanity in terms of our capacity for rational thought. For Plato, this led to the conclusion that we are essentially immaterial minds; whereas Aristotle took a less dualistic stance in defining human beings as “rational animals” [34, 35].

The earliest philosophical definition of personhood comes from Boethius in the early 6th century, who defined a person as an “individual substance of a rational nature” [36, p. 85]. Later in the 17th century, John Locke offered an alternative definition of a person as “a thinking intelligent Being, that has reason and reflection, and can consider itself as itself, the same thinking thing in different times and places” [37, p. 335]. Finally, in the 18th century, Immanuel Kant grounded the incalculable moral worth—dignity—of human persons in terms of the capacity for rational autonomy [13]. By and large, contemporary philosophers have perpetuated the thesis that a person is any being that exhibits a capacity for self-conscious rational thought and autonomous volition, and who is thereby a member of the moral community.8 For example, Lynne Baker contends a person is essentially a being with the capacity for a first-person perspective [38]. Other contemporary theorists cite the following essential activities in which persons engage: rational thought, self-reflexive consciousness, using language to communicate, having non-momentary self-interests, and possessing moral agency or autonomy [39, 40, 41, 42].

Thomistic concept of human nature and flourishing

Another representative and influential thinker in this regard is Thomas Aquinas who, as both a Christian theologian and a synthesizer of earlier Greco-Roman philosophical traditions, continues to be a significant voice in contemporary metaphysical and moral debates regarding the composition of human nature and the proper treatment of human persons.9 According to Aquinas [45, Ia, q. 29, a. 1], every human being is a person, following the Boethian definition quoted above. Being of a rational nature distinguishes human persons from other material substances [46, a. 3; 47, II, ch. 60; 48, I, lect. 10; 48, X, lect. 10]. A human person, though, is not only rational, but is also a sentient, animate, and corporeal substance [49, q. 5, a. 3]. Aquinas thus follows Aristotle in defining human persons as “rational animals” [50, VII, lect. 3]. Rationality, on Aquinas’s view, is the highest capacity found among natural substances because it enables a person to come to know universal conceptual truths and to determine their own actions [45, Ia, q. 29, a. 1]. Hence, he says, the term “person” is attributed to rational beings insofar as they have a special dignity [45, Ia, q. 29, a. 3].

Aquinas refers to human persons as essentially animal because we share certain essential qualities with other members of the animal genus. The primary exemplification of such similarity is the capacity for sense-perception. A human body, though, is unique among other kinds of animal bodies in that it is organized to support not only the capacity for sense-perception, but also the capacity for rational thought. These two capacities are interrelated insofar as the human intellect functions by abstracting universal concepts from “phantasms,”10 which the mind possesses through sense-perception of particular material substances. Since the activity of sense-perception requires proper material organs—eyes, ears, nose, etc.—as well as cognitive functions such as imagination and memory, which Aquinas [45, Ia, q. 78, a. 4] considers to be material functions of the brain, the human intellect requires a well-functioning human body [45, Ia, q. 101, a. 2; 46, a. 2].

With this basic concept of human nature in mind, Aquinas proceeds to argue that the fundamental “good” for human beings consists in our flourishing, which is the fulfillment of our shared nature [45, Ia–IIae, q. 18, a. 5; 45, Ia–IIae, q. 49, a. 2; 45, Ia–IIae, q. 71, a. 1; 51] ]. Human nature is defined by a set of capacities relative to our existence as living, sentient, social, and rational animals—the last including both intellective and autonomous volitional capacities. Human flourishing involves actualizing these definitive capacities of the human species, such that each of us becomes the most perfect—that is, most complete or fully actualized—human being we can be [45, Ia, q. 4, a. 1 ad 1]. To achieve this end, Aquinas claims that all human beings have a set of natural inclinations to pursue whatever we perceive to be good—that is, what is desirable to us insofar as it will help actualize our definitive capacities [45, Ia, q. 5, a. 1]. What he terms the “natural law” includes a set of principles which, if followed, will satisfy a human being’s natural inclinations in accord with reason and thus lead to perfection according to her nature as a human being [45, Ia–IIae, q. 94, a. 2].

The Thomistic account of natural law is premised upon a relatively basic account of human nature of which the primary common features are life, sentience, sociability, and rationality. Of course, each of these features must be further defined, and such definitions, as they become more specific, may be controversial. But a high degree of specification is not required to define certain general natural law precepts. For example, sentience may be understood broadly to refer to human beings’ capacity to sense their environment and respond to it, along with the correlative experiences of pleasure and pain. One could then deduce that depriving a person of any of her senses—say, by blinding her—or causing her unwarranted pain would be bad for her.11 Hence, there is an obligation to avoid intentionally or negligently depriving a person of her senses or causing her undue pain. On the positive side, restoring a blind person’s sight, should she desire it, or causing a pleasurable experience would be good and thus worth pursuing. The question then arises whether it would be advantageous to expand a person’s visual capacity by, for example, genetically or cybernetically modifying her eyes or visual cortex such that she can perceive beyond the current visible spectrum into the infrared and ultraviolet spectra.

Contemporary natural law theorists have cited various goods that arguably follow from the Thomistic understanding of human natural inclinations. John Finnis, for example, identifies seven “basic forms of good for us”: life, knowledge, play, aesthetic experience, sociability/friendship, practical reasonableness, and religion [54, pp. 86–94]. He further specifies that the basic good of life signifies “every aspect of the vitality which puts a human being in good shape for self-determination. Hence, life here includes bodily (including cerebral) health, and freedom from the pain that betokens organic malfunctioning or injury” [54, p. 86].

Aristotelian philosopher Martha Nussbaum has formulated a complementary contemporary framework for moral and political theorizing known as the “capabilities approach.” This approach refers to the intrinsic good of a human being’s individual and, within a given society, collective capacity to act in certain ways that maximize both her individual flourishing and the common good. Nussbaum’s view accords with the Thomistic natural law ethic insofar as both see individual and collective human flourishing as the ultimate goal of moral action and understand this ultimate goal to be reached through the actualization of natural human capabilities.12

Nussbaum lists ten basic, or central, human capabilities, the existence of which exerts moral and political claims upon others to provide the means for their actualization [56, p. 129]. The first two capabilities listed are life and bodily health.13 The latter, of course, is integral to promoting the former, but it also possesses a more extensive value on its own insofar as being healthy also means that one is not suffering from physical disease or injury—recall that our nature as sentient beings, capable of feeling pleasure and pain, is a definitive aspect of human nature according to Aquinas—nor is debilitated in a way that interferes with physical and intellectual activity. In other words, health, along with life, is a basic, foundational necessity for a human person to be able to engage in a maximal degree of activity in pursuit of their individual and, in concert with others, social flourishing: “human abilities come into the world in a nascent or undeveloped form and require support from the environment—including support for physical health and especially, here, for mental development—if they are to mature in a way that is worthy of human dignity” [57, p. 137]. Of course, this does not entail that a person will actually engage in the maximal degree of activity; nor is it incumbent upon society to ensure that they achieve the end of such activity. Rather, society’s obligation is to equip individuals with the opportunity to avail themselves of the tools, with which they are already naturally endowed but may be hampered through disease or disabling injury, to be able to choose for themselves which fulfilling activities they will engage in for their own and others’ benefit.

Transhumanists take this obligation to the next level by contending that individuals ought to have at least the freedom to pursue, if not actually have provided to them by society, non-natural endowments that may either (a) create new capabilities foreign to human nature or (b) allow one to more fully actualize her natural human capabilities. The latter goal accords with the Aristotelian-Thomistic vision advocated by Nussbaum and myself. The aim of a human enhancement, on this view, is not to create a new species—so-called “posthumans”—but rather to facilitate human persons to become the most fully actualized “rational animals” we can be by building upon the inherent potentialities of our extant nature. Forms of enhancement that eliminate naturally-given potentialities, or which add new ones wholly foreign to human nature, will not be conducive to human flourishing by this standard. I will now analyze in detail four particular forms of enhancement that seek to amplify one or more unqualifiedly basic goods that contribute to human flourishing defined Thomistically.

Forms of human enhancement


As noted above, Aristotle defines human beings as essentially “rational animals,” and philosophers from Aquinas to Kant have affirmed that the inherent dignity of human beings stems from our nature as rational and autonomous moral beings. It thus seems that promoting human flourishing, which includes not only the disposition to engage in truth-seeking speculative and practical reasoning but also the ability to do so, should motivate us to utilize all available feasible means to increase our—or our children’s—ability to engage in intellective cognition or have a greater capacity for autonomous volition. As Ryan Anderson and Christopher Tollefsen affirm:

… our given nature is largely one of capacities that require our action to be brought to actuality. Our life must be a life of deliberation, choice, commitment, and action if it is to be a good and flourishing life. We do not want our lives to be lives of merely passive benefit, of induced experiences, but lives of action, lives of which we are agents and authors [58, p. 86].

This perspective, informed by Thomistic natural law theory, does not in principle rule out the moral permissibility of cognitive or other forms of enhancement; in fact, some types of cognitive enhancement may in fact contribute to our being able to more fully actualize our intellective and volitional capacities.14 Nevertheless, Anderson and Tollefsen note two key criteria that need to be satisfied:
  1. 1.

    Enhancements must instantiate more deeply, completely, or thoroughly one of the basic human goods15 without either intentionally damaging other goods or providing us with mere illusions of fulfillment.

  2. 2.

    Enhancements must allow us to instantiate these goods rather than replace our agency with genetic, pharmaceutical, or mechanical alternatives [58, p. 92].


Lubomira Radoilska argues that cognitive enhancement violates these two criteria by (a) diminishing an agent’s “epistemic credit” for her cognitive performance, and (b) altering over time the agent’s attitude toward epistemic achievement [61]. When someone uses a calculator to resolve an algebraic equation, she is not faulted for taking advantage of an available technological shortcut; however, she would not be credited with resolving the equation since she did not utilize her own cognitive apparatus. But perhaps the agent does not mind giving up such credit in favor of being able to resolve complex mathematical equations more quickly and thereby be more productive in applied endeavors. Typically, though, such endeavors are larger, more complicated intellectual projects towards which the cognitive shortcut is but a minor means. The mathematical calculations and applied engineering skills to land a manned spacecraft on the moon remain creditable to the astronauts and NASA engineers despite having benefitted from the assistance of computers and slide-rules. More pernicious, though, is the attitude one may develop as she allows herself to become more and more dependent upon such external aids to conduct her cognitive activities for her, resulting eventually in intellectual “laziness.”

Is this a valid concern with respect to realistic types of cognitive enhancement? Certainly, if a human being were transformed into a true cybernetic organism—“cyborg”16—by means of having had a CPU chip implanted in her brain to take over some or all of her cognitive processing, then credit towards her—even her very existence—as an epistemic agent would be diminished or destroyed altogether. On the other hand, using a pharmaceutical enhancement that assists one to have better focus and attention while performing cognitive operations does not replace, but rather assists the actualization of one’s epistemic agency. Even a technological implant within the human brain that, rather than taking over processing activities, merely helps the brain to access information via direct connection to the Internet or to conduct long-distance communication without the need of any external devices could help expand our perceptual abilities in a way that enhances our intellective functioning [58, pp. 98–99]. One could argue that the use of a pharmaceutical enhancement to achieve greater focus may interfere with the cultivation of the virtue of industriousness by utilizing the drug instead of combatting one’s tendency toward laziness. However, such a drug does not necessarily make one less lazy; rather, someone who elects to take it is disposed to be more industrious and desires the drug’s assistance to combat mental fatigue as opposed to laziness.17

Another type of cognitive enhancement, more permanent in its effects than the use of pharmaceuticals, would involve genetic manipulation to increase the formation of neural connections for the sake of improved memory retention and recall. Memory, Aquinas acknowledges, is a key component of our neurologically based cognitive architecture that is essential for intellective thought to occur [45, Ia, q. 78, a. 4; 45, Ia, q. 84, a. 7].18 Intellective cognition involves the abstraction of universal concepts from the phantasms formed in the imagination as part of the sense-perceptive process. But the intellect does not require phantasms only for its initial act of abstraction, but also whenever it recalls a particular universal or needs to compare a previously abstracted universal with some object currently being perceived to see if it instantiates that universal. All of this requires a well-functioning memory capacity. Of course, the type of memory to which Aquinas is referring is not simply the recollection of data such as facts, figures, and names, but also what is known as experiential memory; the capacity not only to retain information of the first sort, but also to recall past experiences more sharply could feasibly be genetically enhanced given their neurological foundation. Furthermore, face-recognition is a key function of memory that may be subject to deficiency or otherwise open to enhancement beyond the norm; repairing or enhancing this particular memory function could assist one’s sociability, particularly if a person is trepidatious about meeting new people for fear they will not be able to recall their face and/or name on a future occasion and suffer embarrassment as a result.

Cognitive enhancement thus coheres with the Thomistic aim of human flourishing by means of actualizing our rational capacities in pursuit of truth or the accomplishment of practical—that is, technological in the original Aristotelian sense of the term—endeavors. Actualizing such capacities to an improved degree can, in turn, positively impact other valuable human activities, such as forming social relationships. An essential caveat is that epistemic agency must always be reserved to the person herself and not usurped by any external device; nevertheless, reliance on such a device—whether an external hand-held calculator or a neural implant—as a cognitive aid does not necessarily entail surrender of one’s agency.


There are many types of physical enhancement and purposes for which one may seek it. Two of the more problematic types of physical enhancement are performance enhancement for the sake of greater athletic competitiveness, and aesthetic enhancement for the sake of either vanity or increased sexual attractiveness.19 A more beneficial type of physical enhancement, from a Thomistic view of human flourishing, involves factors that contribute to a greater degree of bodily health, which is not only a basic human good in itself insofar as we are essentially corporeal beings, but also instrumentally valuable insofar as illnesses that impair neurological activity have a negative impact on intellective activity [45, Ia, q. 84, a. 7]. Furthermore, increased healthiness, leading to increased longevity, can allow one more time to pursue truth, deepen and develop new friendships, cultivate moral virtue, eliminate moral vice, and contribute to the common good.20

Particular types of physical enhancement that may be permissible, if pursued for these ends and not for the sake of competitive performance, include increased muscle strength, cardiovascular function, lung capacity, bone density, and immune responsiveness [58, pp. 97–98; 59]. Furthermore, enhancement of manual dexterity would benefit individuals such as surgeons or musicians—recall that aesthetic experience is one of the basic goods Finnis cites. Michael Sandel complains, however, that seeking such physical enhancements instrumentalizes health as subordinate to other goals and neglects its value as an end in itself [5, pp. 47–48]. This complaint is based on a false bivalent “either/or” in which health can only be exclusively instrumentally or intrinsically valuable. Rather, as Aristotle notes, some goods can be both intrinsically and instrumentally valuable [62, pp. 7–8]. It is evident that all the various bodily goods, even life itself, fall within this last category: while valuable in and of themselves, they are also instrumentally valuable for the sake of the highest human function—that is, intellective thought and autonomous volition. For instance, while the life and relative health of someone in a persistent vegetative state (PVS) is no less intrinsically valuable than that of someone who is fully conscious and rational, it is nevertheless the case that the PVS patient’s condition is overall not as good as—that is, it is a less desirable mode of existence than—one in which her bodily condition is capable of supporting intellective and volitional activity [63; 64, chs. 3, 5].

Physical enhancement, if pursued for goals commensurate with human flourishing and not merely for the sake of vanity or athletic competitiveness, thus coheres with the Thomistic view of human nature insofar as the bodily functions endemic to our essential animality are both intrinsically and instrumentally valuable by subserving our intellective activity. Hence, as noted above, Finnis and Nussbaum both emphasize health as essentially conducive to human intellectual development. It is important to keep in mind, however, Anderson and Tollefsen’s sound principle that the enhancement of human capacities in pursuit of one or more basic natural goods should not damage our capacity for other basic goods according to human nature. Recall the example cited earlier of physically enhancing someone such that their visual-perceptive range goes beyond the current visible spectrum into the infrared and ultraviolet spectra. While such enhancement might open new possibilities for aesthetic experience, it would likely diminish one’s capacity for aesthetic experience within the natural visible range.21 Since the capacity for aesthetic experience is a basic human good and there is no guarantee that this good will be further enhanced, or at least not diminished, with one’s enhanced eyesight, it would be best to accept one’s visual capacity as naturally given—although allowing correction for any defects.

Another key caveat is that it will be very difficult, if not impossible, to regulate the use of such enhancements once they become available on the open market. Enhancements such as increased cardiovascular function and muscle strength, which augment one’s overall health as well as athletic performance, would likely be utilized for both purposes without any ability to restrict the latter use. The questions at hand are, first, whether allowing performance enhancement in athletics is inherently bad [65]; and, second, whether the potential misuse of physical enhancement should lead to a blanket prohibition on such enhancements altogether, thereby depriving humanity of tremendous potential health benefits and increased longevity.


In morally analyzing various forms of psychological enhancement—including cognitive, emotive, and so-called “moral” enhancement—a common set of normative values are often invoked: autonomy, authenticity, and self-knowledge. Niklas Juth addresses the concern that cognitive or emotive enhancements may alter one’s personality in a way that erodes their autonomy or authenticity. For example, consider a person who has a fundamentally gloomy and cynical outlook on life—though not “clinically depressed”—and elects to utilize an SSRI regimen to generate a more cheerful and positive attitude.22 Juth argues that, so long as this election is autonomously chosen and follows from this person’s desire to have a more positive mood, there is no reason to consider her improved mood to be inauthentic unless one adheres to a “chauvinist work ethics to claim that changes of personality have to be arduous in order to be authentic” [67, p. 43].

Advocates of classical virtue ethics, however—such as Aristotle and Aquinas—argue that the process of cultivating one’s character traits is itself rewarding and one positive consequence is that such traits, once developed, are self-sustaining—that is, they are not essentially dependent on external circumstances to persist. For instance, Bill and Melinda Gates are evidently generous persons and they have had the opportunity to cultivate their generosity on an immense scale by virtue of their Microsoft-based fortune. What if, however, the Gateses lost their fortune due to a severe economic catastrophe? Would they cease to be generous? If they truly have the virtue of generosity, then they would not cease to be generous even if they could no longer operationalize their philanthropic disposition. The proof would be if they were to regain their fortune and re-initialize their philanthropic endeavors, or if they continued to give even when destitute—like the poor widow in the Gospel of Mark (12:41–44) who gave what little she had and not just out of her surplus.

By contrast, an individual who is dependent upon SSRI drugs in order to have a brighter mood will likely not maintain that mood if the drugs were to become unavailable to her. What makes her improved mood inauthentic is that it is neither self-generated nor “owned” by her; rather, it is “given” to her by the drugs, and what is given may also be taken away. However, it may be the case that, having become used to her new positive demeanor and desirous of continuing it, she may be motivated to maintain her new character trait if the drugs become unavailable. Unless, though, the drugs have enacted a stable change in her neurochemistry, she will be back to square one and have to utilize more traditional methods of mood alteration—such as cognitive behavior therapy and positive psychology—which, while involving more effort, may lead to a more stable alteration of her character [68].

This does not mean that SSRIs should not be utilized for individuals whose negative demeanor is wholly outside of their capacity to alter through traditional psychotherapeutic means that are self-driven; nor does it rule out the usefulness of SSRIs as a temporary measure designed to help one realize what she would be like if she were to cultivate a more positive outlook on life and then proceed to do so utilizing self-driven measures. It is important to note that this example is not intended to underwrite the claim that having a more positive mood is inherently good; for having a cynical outlook may be beneficial for someone who is thereby suspicious of others’ motives and thus does not allow themselves to be taken advantage of. On the other hand, one does not have to be a thoroughgoing cynic in order to avoid falling victim to nefarious schemes. Nevertheless, any form of cognitive or emotive enhancement will have to be evaluated from the perspective of whether they are truly beneficial for the enhanced individual and for society in general.

An example of a harmful emotive enhancement would be one that eliminates the experience of suffering altogether or attenuates one’s undesirable emotions such that she becomes blind to goods on which she may be missing out that could be attained only by experiencing such painful emotions. There are a number of spiritual goods—recognized in both Western and Eastern religious traditions—as well as various non-spiritual goods that can result from the experience of suffering. The former include suffering as a means of personal atonement and redemption, or as a sign of personal integrity and honor. The latter include one’s self-fulfillment, her experience of respect and love in solidarity with those who care for her as she suffers, and her exercise of autonomy in responding actively to the otherwise passive experience of pain and suffering [69]. Furthermore, if one becomes inured to the painful emotions that are indicative of ways in which one is not objectively flourishing, the mere elimination of such emotions may lead to a deluded self-perception that one is flourishing when in fact she is not; and the hedonic pursuit of “feeling good” may lead to alienation from one’s “genuine” self. Concern for such a lack of authenticity in one’s emotional life is prevalent among various voices in the enhancement discussion [70, 71, 72].

Although some forms of emotive enhancement may assist one to overcome persistent unpleasant feelings that may inhibit their capacity to pursue happiness or to form healthy social relationships, there is a significantly greater danger, than in the case of cognitive or physical enhancement, of inauthenticity and self-alienation inhibiting one’s autonomous agency, leading to an ersatz form of happiness that is not indicative of actual human flourishing. Furthermore, the experience of emotional suffering, while interfering with one’s natural inclination towards pleasure as a sentient being, may serve an important function in leading to a more genuine and robust experience of happiness that would be derailed by occluding one’s capacity to suffer.

Hence, the prescription of emotive enhancements ought to be scrutinized most carefully on a case-by-case basis instead of being made widely available on the open market. Given, however, the current phenomenon of over-diagnosis of depression and over-prescription of psychotropic drugs [73], it may be too risky to trust that such scrutiny for emotional states beyond clinical depression will be forthcoming. Thus, instead of pursuing emotive enhancement, the focus of psychiatric pharmacology should remain in the realm of treatment for diagnosed pathological conditions that cannot be overcome by more traditional forms of attitudinal and behavioral modification.


Issues related to emotive enhancement also bear on the discussion of so-called “moral enhancement” insofar as it is claimed that “there are some emotions such that a reduction in the degree to which an agent experiences those emotions would, under some circumstances, constitute a moral enhancement” [74, p. 471]. Relevant examples of such emotional tendencies include aggression, xenophobia, and ego-centeredness. Further, it may be possible to positively enhance certain emotional tendencies toward empathy, truthfulness, solidarity, agreeableness, altruism, gratitude, fairness, shame, and forgiveness [74, 75, 76].

No one would assert that an agent must merely accept who they are—in terms of their emotional states that inform their moral motivations—and not strive at all to morally improve oneself; the salient question is how one ought to go about improving one’s moral character. As discussed above concerning emotive enhancement, the relevant issue is not the simple distinction between utilizing “natural” vs. “unnatural” means to alter one’s character. Rather, the issues at stake include which means will have the optimal effect in terms of permanence—or at least semi-permanence—of avoiding dependence upon extrinsic means that may not always be available, and of preserving an agent’s authentic pursuit of genuine human flourishing. With respect to the former concern, recall that one of Aristotle’s criteria for a virtuous action is that it “must proceed from a firm and unchangeable character” [77, p. 1746]. There may not be a sound in principle objection to altering one’s morally relevant emotional states through pharmacological or other means; but it remains to be seen whether this would be the most efficacious means of attaining reliable improvement in one’s moral character.

Consider an individual who is disposed toward impatience but has a desire to cultivate a disposition towards patience. She may utilize a traditional method for altering her response to stressors—for example, when her child is aggravating her, she may leave the room, close her eyes, and count to ten while taking deep breaths—or she may take a hypothetical pill that alters her neurochemistry such that she becomes less prone to becoming aggravated. Does utilizing the latter means decrease the agent’s moral merit in becoming a more patient parent? I contend that it does not inherently decrease her merit insofar as her choice to take the pill comes from the same laudable desire as choosing more traditional means of making oneself more patient. The relevant question is which means would be more efficacious in leading to a sustainable and authentic change of character. Perhaps taking the pill on numerous occasions over time would lead to a permanent change in the agent’s neurochemistry such that she would eventually no longer need to take the pill; but we can only hypothesize at this point whether that would be the case.

A notable concern is that such a pill, once marketed, would be taken for all sorts of reasons, some of which would inhibit, instead of facilitate, an agent’s authentic and stable change of character to become a more patient person. As has been witnessed in the case of anti-depressants and pharmaceutical analgesics—such as oxycontin—it is difficult to regulate the prescription or black-market attainment of such drugs once they are approved. Whether this well-founded concern should lead to a general prohibition of such pharmaceutical enhancements, or whether stricter, more paternalistic, regulations may be called for to ensure that they are being prescribed and utilized properly, warrants further discussion outside the scope of the present analysis.

With respect to the concern that an alteration of an agent’s character be both authentic and effective, Fabrice Jotterand points out that the theory underlying moral enhancement “appears reductive and one-sided” insofar as it focuses on the manipulation of an agent’s motivational and emotional states to the neglect of an agent’s capacity for moral reasoning, which requires knowledge of the content of morality. Importing Alasdair MacIntyre’s [78] contemporary Aristotelian account of moral virtue, Jotterand concludes,

… it appears difficult to determine, on a transhumanist account, what level of emotional control for moral behavior is adequate or what degree of altruism, empathy, or solidarity insures sociability. The way human beings make moral decisions requires the interaction of a complex network of emotional, cognitive, and motivational processes that cannot be reduced just to moral emotions or technological control (moral capacity) but also to practical reasoning (i.e., the source of moral content). [79, p. 7]23

This is not to deny that there is an emotive component to moral virtue. Aristotle, in fact, explicitly defines virtue, in part, as having the appropriate degree of feeling in a given context: “Some vices miss what is right because they are deficient, others because they are excessive, in feelings or in actions, whereas virtue finds and chooses what is intermediate” [62, p. 25]. In applying his general concept of virtue to someone who is brave, Aristotle concludes, “Hence whoever stands firm against the right things and fears the right things, for the right end, in the right way, at the right time, and is correspondingly confident, is the brave person; for the brave person’s actions and feelings accord with what something is worth, and follow what reason prescribes” [62, p. 41].

This passage affirms Jotterand’s complaint that moral enhancement programs capture merely one aspect of the cultivation of an agent’s moral character. For no type of enhancement could rightly inform someone of what the moral worth of some end may be, or what would be the most appropriate means toward achieving that end. At best, a manipulation of one’s aggressive tendencies may help moderate their reaction such that they are less prone to act rashly; but there will be a corresponding danger of eliminating one’s aggressive tendencies altogether, which would preclude one’s ability to act bravely in appropriate contexts.

Not all proponents of moral enhancement, however, suffer from the narrow focus that Jotterand properly accuses others of holding. An interdisciplinary “Genetic Virtue Project”—involving philosophers, psychologists, and geneticists—is seeking to discover ways in which forms of genetic manipulation may complement, not replace, the Aristotelian model for virtue acquisition:

Thus, the hope of the GVP is not to make persons virtuous but to make them better equipped to learn how to be virtuous. In this sense, the GVP is in agreement with Aristotle’s view that “the virtues arise in us neither by nature nor contrary to nature; we are naturally receptive of them, but we are completed through habit.” To this it may be added that some people are more naturally receptive, that is, able to learn, than others. [81, p. 39]

Understood in this way, it may indeed be possible to positively assist certain individuals to cultivate moral virtue by enhancing particular emotional states or facilitating the practical reasoning process when limited by neurological constraints [82, 83, 84]. Nevertheless, the same cautions noted above with respect to emotive enhancement more broadly remain applicable and it may be difficult to ascertain—both externally and subjectively—whether one is being helped to cultivate virtue through their own efforts of practical reasoning and psychological self-mastery or being offered a mere simulacrum of true moral virtue. As noted above, the risk of inauthentic cultivation of moral virtue may be simply too difficult to avoid due to the inherent inability to effectively regulate access to various forms of enhancement once they become marketable.


An unbridled, perfectionist, drive toward human enhancement is not compatible with the Thomistic concept of human nature and flourishing insofar as it is not premised on an objective view of what constitutes human well-being, such that certain enhancements may be pursued for misplaced goals—such as vanity or competitiveness—or lead to an ersatz form of “happiness.” Nevertheless, certain forms of human enhancement, aimed at improving the extent to which our bodies support the actualization of essential human capacities, may facilitate an asymptotic progression towards individual and collective flourishing. As noted above, the first principle of the natural law, according to Aquinas, is to pursue the good, which is what is desirable insofar as it is perfective—asymptotically speaking—of human beings according to our nature as rational animals [60].

Hence, cognitive or physical enhancements may be licitly utilized in pursuit of augmented capacities that are conducive to human well-being as living, sentient, social, and rational animals. The potential for misuse will unavoidably be present, however, and thus careful monitoring is warranted. Emotive or moral enhancements, on the other hand, must be approached much more cautiously so as not to erroneously replace the genuine cultivation of virtue with more-or-less “programmed” moral behavior. The risk here is profound as the diminishment or loss of moral agency undercuts the very foundation—as recognized by Thomists, Kantians, and others—of the inherent dignity of human persons. Nevertheless, there are definite material limitations to the exercise of human beings’ intellective and volitional capacities that call for cautious continued modification beyond the current “given.”


  1. 1.

    Relatedly, I will not entertain any theological premises in my analysis that may support or weaken the principled case for human enhancement. Rather, acknowledging that what I will describe is one aspect in which human beings can be understood as created in the “image and likeness of God” (Genesis 1:27), I will focus only upon Aquinas’s philosophical account of human nature and flourishing.

  2. 2.

    An excellent fictional presentation of such a bifurcated society due to genetic engineering is Andrew Niccols’s film Gattaca (Columbia Pictures, 1997).

  3. 3.

    An example of a group who generally approves of any form of enhancement is the World Transhumanist Association, also known as “Humanity+” [6]. General critical assessments of enhancement technologies are developed by Michael Sandel [5] and Jürgen Habermas [7]; Frances Kamm [8] and Elizabeth Fenton [9] offer critical responses to Sandel and Habermas, respectively. The President’s Council on Bioethics [10] provides a comprehensive evaluation of various forms of human enhancement.

  4. 4.

    Descriptions of various present and potential near-future means by which forms of enhancement may be brought about can be found among the contributions to [12].

  5. 5.

    The primary historical proponent of the libertarian concept of autonomy is John Stuart Mill [14]. Robert Nozick [15] articulates an influential contemporary defense of libertarianism.

  6. 6.

    Gerald McKenny [27] and Sandel [5, ch. 5] critique human enhancement on the basis of the value of appreciating our vulnerability and the attendant virtues we may cultivate in response.

  7. 7.

    Discussion, both pro and con, of these objections can be found in [7, 28, 29, 30, 31, 32].

  8. 8.

    This general definition captures the essence of being a person, but omits many distinct nuances that are often contested. For example, it is debated whether having a capacity for self-conscious rational thought and autonomous volition requires having a biological cerebrum, or whether a functionally equivalent silicon information-processing system would suffice. Also debated is what is required to be a member of the moral community. For example, a severely mentally disabled human being may not be a contributing member of the moral community—in that she does not have the mental capacity to fulfill duties to others—but may be a recipient member—in that she has rights which entail others fulfilling duties toward her.

  9. 9.

    As Thomistic thought has been a primary influence upon the moral theology of the Roman Catholic magisterium, which in turn has been a significant conservative voice in many bioethical debates, it is worth noting what Catholic authorities have had to say on the subject of genetic enhancement. The Vatican’s Congregation for the Doctrine of the Faith wholly rejects any form of non-therapeutic genetic intervention [43]. Pope John Paul II, however, offers a more open-ended assessment in which he defines four basic criteria that, if satisfied, would allow for the moral possibility of genetic enhancements [44]. While it may be the case that no human enhancement project could avoid violating one or more of those criteria, perhaps some forms of enhancement may be appropriately carried out that both fulfill the criteria while also avoiding the concerns raised by the Congregation.

  10. 10.

    The purpose of phantasms is to be available for the intellect to use in abstracting the intelligible form—that is, the universal essential concept—of perceived things. Hence, phantasms are between the immediate mental impression of an object perceived by sensation and the intellectual understanding of that object’s nature as abstracted from any individuating characteristics.

  11. 11.

    The fundamental good of promoting pleasure and avoiding pain for both oneself and others is also affirmed by non-natural law moral theorists, most notably utilitarians Jeremy Bentham and John Stuart Mill [52, 53].

  12. 12.

    Nussbaum and Aquinas also agree that such actualization is achievable through just interpersonal and social relationships defined in terms of our moral obligations to each other, which in turn is the foundation for rights and duties. It is not surprising that Nussbaum’s and Aquinas’s views cohere insofar as Aquinas was significantly influenced by reading and commenting upon Aristotle, quoting him at length as “The Philosopher” [55, ch. 12].

  13. 13.

    Nussbaum likens her approach to Rawls’s notion of “primary goods”; although she also criticizes Rawls’s approach as inadequate for responding to the diversity of human needs.

  14. 14.

    Among the authors cited in this paper, Anderson and Tollefsen, James Delaney, and James Keenan address the topic of human enhancement from a Thomistic perspective as well [58, 59, 60]. Each of their analyses differs from the present analysis, however, in various ways. Anderson and Tollefsen adopt a Thomistic anthropological and ethical framework, but they do not relate their analysis explicitly to Aquinas’s texts; furthermore, they arrive at a more pessimistic conclusion regarding some forms of cognitive enhancement that, according to my analysis, can serve as an aid to the “self-constituted philosopher’s” search for wisdom [58, p. 96]. Delaney conducts his analysis in light of magisterial documents of the Roman Catholic Church, which, although informed by Thomistic philosophy, are also based upon fundamentally theological premises not referenced in the present analysis; furthermore, Delaney discusses genetic enhancement only in general terms without specifically analyzing distinctive forms of enhancement. Finally, similar to Delaney, Keenan approaches the topic from an explicitly theological perspective and focuses narrowly on the question of whether enhancement involves a misguided striving toward perfectionism.

  15. 15.

    The authors have in mind here a list of basic goods quite similar to Finnis’s list cited above.

  16. 16.

    Fictional depictions of cyborgs include the Terminator, the Cylons of the re-imagined Battlestar Galactica television series, and the Borg of Star Trek: The Next Generation and Star Trek: Voyager.

  17. 17.

    I am grateful to John Boyer for raising this criticism.

  18. 18.

    Aquinas argues that intellective cognition can occur post-mortem without one’s body; but such is not the natural mode of human cognition [45, Ia, q. 89].

  19. 19.

    Discussion of the various pros and cons of performance enhancement can be found in [12, pt. IV]

  20. 20.

    I will not discuss here the potential benefits and problems associated with expansively increased longevity, asymptotically approaching immortality.

  21. 21.

    Consider the fictional depiction of a human being with technologically enhanced eyesight in the television series Star Trek: The Next Generation. The character Geordi LaForge, congenitally blind, is capable of seeing well beyond the visible spectrum thanks to his VISOR. In the feature film, Star Trek: Insurrection (Paramount Pictures, 1998), Geordi’s natural eyesight is temporarily restored and, in a moving scene, he sees a sunrise naturally for the first time, telling his captain, “You know, I’ve never seen a sunrise—at least not the way you see them.”

  22. 22.

    To be sure, there is some debate whether SSRIs are an effective means of effecting long-term emotive enhancement [66].

  23. 23.

    Maartje Shermer, also employing a MacIntyrean virtue-theoretical framework, defends a contrary view [80].



A version of this paper was presented at the 2013 Oxford Symposium on Religious Studies, the UNESCO Chair in Bioethics 9th World Conference, the 3rd Annual Conference on Medicine and Religion, the 23rd Annual Meeting of the Association for Practical and Professional Ethics, the 2013 meeting of the Notre Dame Center for Ethics and Culture, and the first U.S. meeting of the Pontifical Academy of St. Thomas Aquinas at the University of St. Thomas in Houston. I am grateful for comments provided by audience members at each of these conferences as well as to two anonymous reviewers for this journal.


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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Semler Endowed Chair for Medical Ethics, College of Osteopathic MedicineMarian UniversityIndianapolisUSA

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