Among his immensely rich academic work, Arvind Sharma dedicated one of his more than forty monographs to the controversial issue of interreligious comparison.Footnote 1 While for decades the comparative method had been viewed as essential, often providing the name (“Comparative Religion”) to the discipline that is now mostly called “Religious Studies,” it became subject to severe, almost devastating critique as part of the wave of postmodern ideologies which turned against any kind of wider or “grander” perspectives (excepting, of course, their own universal claims). As a result, Religious Studies widely abandoned investigations that are explicitly comparative (implicitly, the comparative dimension could and can never be fully eliminated) in favor of narrow localized studies.Footnote 2 The main charge is that interreligious comparison necessarily loses sight of the allegedly incomparable uniqueness of the individual phenomenon, which, allegedly, can only be properly understood if seen exclusively within its own specific context. The different contexts are said to be incommensurable so that even an indirect comparison of religious phenomena—via a comparison of their respective contexts—is held to be impossible or, if nevertheless undertaken, as leading inevitably to distortion and misunderstanding. Against this background, and in contrast to it, Sharma boldly defends “the claim that one religious tradition helps in understanding another, that a knowledge of tradition A helps us understand tradition B better, and that the resulting phenomenon of enhanced understanding may be described as one of ‘reciprocal illumination’” (2005: 3).

In this essay I will first briefly discuss Sharma’s concept of “reciprocal illumination.” Secondly, I will relate this concept to the observation that religious diversity is apparently not entirely random, but displays recurrent patterns and structures that may be described as fractal. Thirdly, and finally, I will point out how Sharma’s concept, seen in conjunction with a fractal interpretation of religious diversity, has great potential within the growing field of interreligious theology.

Reciprocal Illumination

According to Sharma (2005: 55, 2018: 181), sensible and illuminating comparisons can be applied to both specific religious data or phenomena and larger religious traditions to which such data belong. He thus sketches a wide field for the meaningful application of comparative investigations: One may compare different data/phenomena within one particular religious tradition or between traditions, or compare several traditions or particular groups and types of traditions (Sharma 2005: 113–59). In addition, it can also make sense to compare data and issues in relation to religion and the secular realm (Sharma 2005: 161–79). Regarding the question of who will be enlightened by means of such comparisons, Sharma holds that this can be both, insiders and outsiders to the respective religions (2005: 49–50, 53, 71), although in this book his attention is primarily on that kind of “outsider” who is a religious studies scholar (53). He therefore distinguishes

between a first-order reciprocal illumination, which forms a part of religious experience itself, and a second-order reciprocal illumination, which belongs not to the world of religious life and religious experience but to the study of such religious life and experience, which is now regularly carried out in the branch of humanities under several names but most often under the rubric “religious studies” or “the study of religion” (Sharma 2005: 43; emphasis in the original).

Unfortunately, Sharma does not expound on the case of “scholar practitioners” or “theologians” of the various religious traditions who study religions according to academic standards but do so in the religions’ genuine interest of achieving a better and deeper understanding of religious life as it flows through their own and the others’ traditions.Footnote 3 It is this particular kind of study to which I will relate Sharma’s ideas in the third section of my essay.

While Sharma adopts a rather broad position in relation to the questions of where comparative methods can be applied and to whom such comparisons might be illuminating, he is more restrictive in defining what constitutes a meaningful comparison. Here he makes a sharp distinction between “homonymous” and “synonymous” comparisons:

Homonymous comparisons are between phenomena, which appear similar but are really different, just as homonyms are words with similar sounds but with different meanings. Synonymous comparisons are between phenomena that appear different but possess similar significance in each tradition, just as synonyms are words that have different sounds but are similar in meaning. Old comparative religion has been oriented toward making homonymous comparisons, but new comparative religion—at least, the kind I would like to practice—will be oriented toward making synonymous comparisons. Now, when synonymous comparisons are made between two traditions, they often result in what I like to call reciprocal illumination. That is to say, one tradition sheds light on the other (Sharma 2005: 25).

Sharma thus endorses part of the critique of older forms of interreligious comparisons which too often, so the objection goes, have taken individual religious phenomena out of their generic context and assembled them under transreligious categories or types. In contrast, Sharma is interested in such comparisons where the compared objects “shed light on another,…rather than on a common or transcendent category.” Such comparison is not meant “to illuminate anything other than the data themselves” (Sharma 2005: 254). Reciprocal illumination “dispenses…with the role of the mediating category (such as sacred space, etc.) that is utilized in the thematic study of religion” (Sharma 2005: 64). This dispensation, as Sharma underlines, is due to his intention to avoid the distorting tendency of homonymous comparison. He therefore

shares W. C. Smith’s concern regarding phenomenological typologies, “namely that a deep knowledge and understanding of two particular traditions may lead to the recognition that authentic comparison need not necessarily follow typological lines—for example, the sacred text of one, the Qur’ān, may be equivalent to the sacred founder of another, Christ” (Sharma 2005: 89, citing Whaling 1984: 219).

As a further example, Sharma discusses the homonymous comparison of Christ’s and Milarepa’s resurrection which, despite a number of typological similarities, may nevertheless be highly misleading. For, whereas Christ’s resurrection is constitutive to Christianity, Milarepa’s resurrection does not stand in the same constitutional relation to Buddhism. In Buddhism, the constitutive role lies with the teaching of the Buddha as a result of his enlightenment. A meaningful, that is, reciprocally illuminating comparison would thus have to be a synonymous one, comparing Christ’s resurrection with the Buddha’s enlightenment (Sharma 2005: 31–32). As with the example of Christ and the Qur’an, a synonymous comparison becomes possible—and illuminating—by focusing on structural analogies (Sharma 2005: 86) or functional equivalentsFootnote 4 regarding the respective data. Thus, Sharma’s caution against categories and types does not dismiss the consideration of similar structures. On the contrary, one first needs to identify the structural and functional place of the data within their respective systems before one can advance to a synonymous comparison.

But then, how do the different religious systems relate to each other? And can they be properly regarded as systems at all? Over the past five decades, fostered by the work of Wilfred Cantwell Smith, attention has been increasingly drawn to the fact that none of the major religions is a homogenous entity. Instead, each of them constitutes a multifaceted “cumulative tradition” (Smith 1962), which is not only internally highly diverse, but also undergoes significant transformations in the course of history. Sharma pays some attention to the systematic or structural differences between different “types of traditions” (2005: 149–59) and to the internal diversity within each one of them (113–15). In dealing with the typological distinction between prophetic traditions and wisdom traditions, he makes the interesting observation that “the way the traditions are grouped changes with the criteria used” (Sharma 2005: 153). But he does not pursue any further what this tells us about the complex nature of the traditions and how to understand the possibility of different groupings in terms of structural analysis. This is where fractal theory comes in.

Fractal Patterns in Religious Diversity

Is religious diversity entirely random and chaotic, or does it display a certain order and recurrent structural patterns? In the early days of Religionswissenschaft (“Science of Religion”), the founding figures and pioneers of the new discipline, especially those from the phenomenological school, were keen on exploring the nature and structure of religious diversity and employed interreligious comparisons as one of its major tools. Today, in the wake of poststructuralism, the quest for structural patterns in religious diversity has become as unpopular as the comparative method. And the arguments are the same. For example, in a recent study on the Buddhist distinction between “worldly” (laukika) and “other-worldly” (lokottara), one reads:

It may well be felt speculative cross-cultural comparisons premised upon the assumption that similar binary schemes manifest in different times and cultural settings is doomed to over-simplification and some degree of distortion.…Partly in attempts to account for this cross-cultural appearance, certain academics have chosen to push discussion into the realm of universals (or related concepts), seeking to associate the scheme with other binary divisions—religious–secular, spiritual–profane, transcendent–immanent. The suggestion has been that, either due to the structure of human society or the human mind, the reappearance of such a division is inevitable.…The universalistic path inexorably draws one away from the specifics, not least because it forces us to move outside the realm of traceable historical and textual pathways (Samuels 2019: 241, 256, 257).

None of such arguments, however, comes anywhere near the production of real counterevidence against the existence of universally identifiable structures. Moreover, the warning of possible oversimplification and negligence of the specifics itself presupposes a comparative perspective. Otherwise, specifics could hardly be discerned as such. And the discovery of similar structures and patterns by no means excludes individual specifics as elements within such structural similarities.

In their quest for structural commonalities, pioneers in Religious Studies focused primarily on global interreligious diversity, and less so on the intrareligious diversity as it appears within each religious tradition, and still less so on the intrasubjective religious diversity as it is found in many a religious believer. The latter is manifest either diachronically, in individual religious biographies (people traversing through different types of religiosity in the course of their lives), or synchronically, in various forms of hybrid religious identities. We can thus distinguish three principal levels of religious diversity: the macro-level of interreligious diversity, the meso-level of intrareligious diversity and the micro-level of intrasubjective religious diversity, while each of the smaller levels constitutes a component of the larger one. In the 1970s, the mathematician Benoît B. Mandelbrot (1983) coined the term “fractals” for patterns which are self-replicating over different scales. That is, the pattern replicates itself at several levels of its components. While various geometrical structures show a strict self-similarity over different scales (as, for example, the well-known Sierpinski triangle), there are numerous phenomena in organic and inorganic nature that display fractal patterns of rough self-similarity. The small florets that together form a cauliflower or the small leaflets that together form a fern leaf are never exactly identical to the larger structure, or to one another, but they clearly replicate a similar pattern. Some philosophers have made analogous observations regarding cultural diversity, whereby prominent features of intercultural diversity reappear in intracultural diversity. I suggest that this also applies to the realm of religious diversity: A number of differences between the major religious traditions (macro-level) reappear in modified form at the meso-level of intrareligious diversity and are even found at the micro-level of intrasubjective religious diversity.Footnote 5

Some phenomenologists had already come close to making this observation. As early as 1932, the German scholar, Hilko Wiardo Schomerus, distinguished four major types of religion: (1) religions of the law (for example, Judaism), (2) magical-sacramental religions (“Indian mysticism”), (3) gnostic religions (Greek Gnosis and Buddhism), and (4) devotional religions (Hindu bhakti traditions and some forms of Mahāyāna Buddhism) (1932: 22). According to Schomerus, these types correspond to the Hindu distinction of four ways: the way of works (karmamārga), the way of meditation (yogamārga), the way of knowledge (jñānamārga), and the way of devotion (bhaktimārga). Yet while these distinctions are applicable to different types of religions, they are also applicable to different strands within each type of religion. He thus concluded: “Religion as such is hypostasized in a few major types, which persistently recur and unfold everywhere in similar ways, bringing about in all places kindred forms and formations” (Schomerus 1932: 26; my translation). In the 1980s Hans Küng and Julia Ching made a similar observation, albeit using a different typology. Distinguishing prophetic (Judaism, Christianity, Islam), mystical (Hinduism, Buddhism), and sapiential (Confucianism, Daoism) religions, they found that each of the religions of one specific type also contains features and elements of the other types (Küng and Ching 1989: 15–17). Likewise, John A. Hutchison distinguishes between cosmic, acosmic, and historical religions, associating, for example, the first type with “prehistoric and folk religions,” the second with “philosophic Hinduism,” and the third with “monotheism” (1991: 16–18). Yet he too adds that “the differences implied by the threefold classification of religions by no means preclude the possibility of similarities of many sorts extending across the boundaries of the types” (Hutchison 1991: 17). John B. Cobb adopted Hutchison’s classification and made the same point, stating that “more than one of these types can be discerned in most of the great traditions” (1999: 121). Such observations support the conjecture that religious diversity displays fractal patterns, regardless of which typology is employed.

Similar observations have been made by some Eastern religious thinkers as well. As has been pointed out by Ayon Maharaj, Svāmī Vivekānanda held that there are four paths leading to the realization of the highest goal, “those of work, love, psychology, and knowledge” (2018: 120, citing Vivekananda 1989, 1: 108), based on the traditional Hindu distinction between karma-, bhakti-, raja-, and jñāna-yoga (1989, 8: 152–55). While Vivekānanda claimed that each religion reflects one of these ways (1989, 8: 152), he also held that each religion contains elements of the others and that such features are also expressed at varying degrees in religious individuals (Maharaj 2019: 109–10). An analogical point was made by the Thai-Buddhist reformer, Bhikkhu Buddhadāsa. Building on the traditional Buddhist distinction between paññādhika (wisdom dominated), saddhādhika (confidence dominated), and viriyādhika (willpower dominated) ways to awakening, he sees Buddhism as being focused on wisdom, Christianity on faith/confidence, and Islam on willpower. “Thus each of the three religions has one of the three paths as its special characteristic” (Buddhadāsa 1967: 13). Yet he immediately adds: “But strictly speaking, none of the above religions provides only one of the paths mentioned; each religion comprises all three ways; the only difference is that a certain religion may give preference to one way or the other” (Buddhadāsa 1967: 13).

In the case of Vivekānanda and Buddhadāsa, their observation of fractal patterns enhanced their positive appreciation of religious diversity in general, and of specific other religions in particular. This was because they both regarded the distinguishing categories, features, or “paths” as complementary rather than contradictory. According to Vivekānanda, each of the four yogas “blends into the other” and “in the end, all these four paths converge” (Vivekananda 1989, 1: 108). Likewise, Buddhadāsa holds that the three paths are “complementary” and “can merge smoothly” (1967: 14). One may assume that for both thinkers, this implied that in and through the actual encounter between people from different religious traditions something like reciprocal illumination and mutual learning may take place. But in what sense can the existence of fractal patterns explain the occurrence of reciprocal illumination and how may their discovery foster mutual learning? These are the questions to which I will now turn.

Reciprocal Illumination and Interreligious Theology

Today, interreligious encounters occur at an unprecedented rate. As we all know, such encounters can take various forms ranging from open conflict or latent tension at the one end of the spectrum to constructive cooperation and reciprocal learning at the other. Correspondingly, communication between religious communities and/or individuals can range from aggressive, distorting polemics to sympathetic attempts at mutual understanding, from invasive proselytization to the joint effort to gain deeper insight into human existence in light of transcendence. Interfaith dialogueFootnote 6 can be distinguished from polemics and apologetics in so far as dialogue is not primarily interested in the weaknesses of the other’s faith (in order to demonstrate the superiority of one’s own), but in the other’s strengths so that one may learn from them. “The primary purpose of dialogue,” as one of its Christian pioneers once phrased it, “is to learn, to change and grow in the perception and understanding of reality and then to act accordingly” (Swidler 1990: 43).

More recently, especially after 9/11, interreligious dialogue has often been viewed as a form of interreligious diplomacy or a form of ongoing crisis prevention curbing the potential for interreligious conflict. While these are certainly honorable aims, the original interest in interreligious learning was of a different nature. Fortunately, this interest has not been lost but now often continues under new labels such as “comparative theology” or “interreligious theology.” While scholars use these labels in different ways, some seeing more and others less of a difference between the two, they share the ideal of genuine religious learning through insights arising from comparative/interreligious studies. This is where Sharma’s reflections become pertinent, for he too views comparison as a way to improve our understanding of religions and hence as a way of learning, terming the effect of such learning “reciprocal illumination.” According to Sharma, reciprocal illumination, as it happens between two religious traditions, can take three forms: “memory, recognition, or potentiality” (2005: 67, 68). “Memory” refers to the rediscovery, triggered by comparison, of some forgotten feature of one’s own tradition. “Recognition” signifies a kind of immediate awareness of a substantial parallel. “Potentiality” denotes the recognition of some hitherto undeveloped potential that is seen as more fully manifested in another tradition.

In two recent studies, Catherine Cornille (2016, 2020) has helpfully identified six principal forms of interreligious learning: (1) intensification (reinforcement of truth through the discovery of significant parallels), (2) rectification (overcoming misunderstandings and distortions), (3) recovery (rediscovery of neglected, marginalized, or ostracized elements of one’s own tradition), (4) reinterpretation (a fresh understanding of one’s own tradition by seeing it through the framework of another tradition), (5) appropriation (adoption of elements from other traditions), (6) reaffirmation (“learning as reaffirmation of one’s own beliefs and practices in light of alternative religious views”; 2020: 141).Footnote 7

Four of Cornille’s six types of interreligious learning resonate strongly with Sharma’s three forms of reciprocal illumination: Cornille’s “recovery” is more or less identical to Sharma’s “memory.” Cornille’s “intensification” is fairly close to Sharma’s “recognition.” And what Cornille calls “reinterpretation” and “appropriation” falls easily under Sharma’s category of “potentiality.” The possibility of such forms of interreligious learning in terms of reciprocal illumination can be well explained by the existence of fractal patterns. As has been said above, the most prominent feature of fractal patterns is their recursiveness over several levels or scales. In relation to religious diversity this implies that some patterns by which we distinguish different types of religions at the macro-level reappear at the meso-level of intrareligious diversity and can even be detected at the micro-level of individual people. This implies that there will be significant similarities across the meso-level of intrareligious diversity. The otherness of another religion will be to some extent akin to certain forms of otherness known from within one’s own religion. And the same applies to commonalities. However, commonalities and differences often appear in the other religion under different names, with different emphases, and, most importantly, in different configuration or a different location within analogous (functionally equivalent) structural webs. It is, to quote a musical metaphor used by Hutchison, as if there were several “main keys in which religions are composed, but in these keys a great many themes and images recur” (1991: 17).

Within this kind of constellation, it is quite likely that comparative studies produce learning effects such as “recovery”/”memory,” “intensification”/”recognition,” and “reinterpretation”-“appropriation”/”potentiality.” “Memory” and “recognition” will probably never indicate exact identity of the phenomena under comparison but similarity in difference, the difference often being the result of a different arrangement. It is this kind of difference that carries the “potentiality” of reinterpretation and adaptation. Reinterpretation explores the possibility of looking at one’s own tradition, or certain elements within it, “through the categories or philosophical framework of another” (Cornille 2020: 129), that is, in the light of a different arrangement. While reinterpretation therefore involves some kind of adaptation of one’s own beliefs to some other conceptual framework, appropriation implies the importation and integration of something new into an existing framework within one’s own tradition. Both forms of learning presuppose some sort of fractality in as much as there must be some potential or affinity within one’s own tradition that allows for the adaptation to a new framework, and there must be some potential or affinity that makes an existent framework receptible for such integration. There need to be some receptors to which the new elements can be connected. The undeveloped or underdeveloped aspect that enables these types of learning is a structural “potentiality” of one’s own tradition. Yet it is also evident that through processes of adaptation and integration existing fractal patterns expand, change, and undergo further diversification.

Additional insights can be gained if we consider, in the light of fractal theory, Cornille’s two remaining types of interreligious learning: reaffirmation and rectification. If central features of interreligious diversity reappear as intrareligious diversity (or vice versa), parallel assessments of the intra- and the interreligious other become likely, both positive and negative. During the Christian Reformation, Lutherans accused Catholics of the heresy of justification by works of the law, and they leveled the very same accusation at Judaism and Islam. Conversely, the Catholic Jesuits held that Satan had inspired the same heresy (salvation by faith alone) in Luther as in the founders of Japanese Pure Land Buddhism. Thus, in both cases a similarity was perceived between the intra- and the interreligious other and the negative assessment of the intrareligious other was transferred to the interreligious other. However, a positive assessment would also be feasible. In the “Joint Declaration on the Doctrine of Justification” of October 1999, Lutherans and Catholics reciprocally acknowledged the fundamental value and legitimacy of the teachings of the other and restricted their mutual condemnations to extreme or one-sided versions of the respective teachings. In essence, this implies that a fundamental compatibility exists between the work of divine grace and corresponding human works: “the Lutheran and the Catholic explications of justification are in their difference open to one another” (“Joint Declaration,” paragraph 40). If similar hermeneutical efforts were extended to the interreligious other, Catholics would be more appreciative of teachings of salvation by other-power, as found in the Buddhist Pure Land tradition, and Protestants would be more hospitable to the emphasis on works of righteousness in Judaism and Islam as embedded in the foundational trust in divine mercy and forgiveness. All this would become possible by a heightened awareness that the polarity of self-help and other-help demarcates differences both between and within traditions. And if in relation to intrareligious diversity this polarity can be assessed as being complementary instead of contradictory, then such complementarity can also be applied to interreligious diversity.Footnote 8

In light of these remarks the type of learning that Cornille terms “reaffirmation” appears somewhat ambiguous. As she herself admits, “this reaffirmation may seem reminiscent of traditional apologetics” (Cornille 2020: 138). And this impression is not tempered but rather enhanced when Cornille cites Paul Williams’s record of his reconversion from Buddhism to ChristianityFootnote 9 as an example of this type of “learning.” As she notes, Williams’s reaffirmation of Christian beliefs is “informed by the Buddhist teachings against which they are reaffirmed” (Cornille 2002: 139; emphasis added). Cornille is certainly right in suggesting that “reaffirmation” of one’s own beliefs can be in some way the outcome of a number of dialogical processes. Yet, saying that reaffirmation is “deeply informed by the religious other” (Cornille 2002: 140) is not enough. For it makes a significant difference whether such informed reaffirmation still happens in a confrontational mode against the religious other or if the reaffirmation occurs in the ecumenical spirit of recognizing one’s own beliefs as part of a larger, complementary setting.Footnote 10 In the “Joint Declaration” mentioned above, Lutherans and Catholics certainly reaffirmed their beliefs, yet they did so no longer in the mode of reciprocal condemnation but as part of a larger consensus. In such cases, reaffirmation happens in correspondence with a positive change of one’s former negative assessment of the other and not as a simultaneous reaffirmation of the other’s rejection. In Cornille’s terminology, it concurs with “rectification.” This, however, is only possible if what were once viewed as irreconcilable opposites are now perceived as complementary polarities.

The observation of fractal patterns in religious diversity is as such open to both types of assessment, a reaffirmation of antagonisms or a discovery of complementarity. But it also explains why the latter is a genuine option. This can be illustrated by the above-mentioned examples of Vivekānanda and Buddhadāsa. They both drew on schemata that permitted a positive evaluation of diversity within their own religious traditions (the scheme of four yogas in the case of Vivekānanda and that of three inclinations, adhikas, in the case of Buddhadāsa) and transferred the legitimacy of such intrareligious diversity to the interreligious field, thereby presupposing a fractal structure of diversity. Moreover, both Vivekānanda and Buddhadāsa viewed the respective differences as complementary—regardless of whether this was seen as a form of hierarchical complementarity, as has often been the case in their traditions (that is, ranking the four paths or inclinations), or as a complementarity on an equal level as at least some statements of Vivekānanda and Buddhadāsa suggest.

Interreligious comparison that leads to the observation of fractal patterns in terms of complementary differences appearing both within and between traditions can be regarded as a further expansion of what Sharma calls a synonymous comparison: It is the synonymy or functional equivalence not of particular data or phenomena occupying a comparable place or significance within different traditions, but the synonymy of similar differences/distinctions within and between them. How can we account for the existence of such fractal patterns? In pursuing this line of inquiry, the incorporation of the micro-level of intrasubjective diversity becomes inevitable. I deem it likely that the diverse manifestations of religious ideas and practices are rooted in the structures of the human psyche and the human mind, as has been assumed by William James with regard to the former and Rudolf Otto with regard to the latter. Neither the human psyche nor the human mind seems to be a tabula rasa. And the universality of their basic structures may explain why human beings relate to transcendent reality in different but recurrent patterns, as much as it would explain the existence of fractal structures in cultural diversity.

This account of religious diversity could be read along the lines of a projection theory à la Ludwig Feuerbach. But this reading is not the only possibility. It can also be read along the traditional lines that posit a micro-macro cosmic scheme of diversity in which transcendent oneness is both hidden and apparent (Jackson 2004: 19–84). If religions learn through serious interreligious studies to understand themselves as a unique, internally diverse, but equally valid part and component of this legitimate larger diversity, their self-awareness and self-understanding are changed in a dramatic yet highly beneficial way. This may be viewed as the climax of the learning type of “rectification,” involving “the restoration or proper understanding of the other, and thus a new understanding of one’s own tradition” (Cornille 2020: 121).Footnote 11 I suggest that this is the ultimate promise of what Arvind Sharma has so aptly called “reciprocal illumination.”