Psychology’s exceptional position among the sciences and its key problems can be traced to its study phenomena’s peculiarities and the conceptual and methodological challenges they entail.
Experience: Elementary to All Empirical Sciences
Experience is elementary to all empirical sciences, which are experience-based by definition (from Greek empeiria meaning experience). The founder of psychology, Wilhelm Wundt, already highlighted that every concrete experience has always two aspects, the objective content given and individuals’ subjective apprehension of it—thus, the objects of experience in themselves and the subjects experiencing them. This entails two fundamental ways in which experience is treated in the sciences (Wundt 1896a).
Natural sciences explore the objective contents mediated by experience that can be obtained by subtracting from the concrete experience the subjective aspects always contained in it. Hence, natural scientists consider the objects of experience in their properties as conceived independently of the subjects experiencing them, using the perspective of mediate experience (mittelbare Erfahrung; Wundt 1896a). Therefore, natural scientists develop theories, approaches and technologies that help minimise the involvement of human perceptual and conceptual abilities in research processes and filter out their effects on research outcomes. This approach is facilitated by the peculiarities of natural-science study phenomena (of the non-living world, in particular), in which general laws, immutable relationships and natural constants can be identified that remain invariant across time and space and that can be measured and mathematically formalised (Uher 2020b).
Psychologists, in turn, explore the experiencing subjects and their understanding and interpretation of their experiential contents and how this mediates their concrete experience of ‘reality’. This involves the perspective of immediate experience (unmittelbare Erfahrung), with immediate indicating absence of other phenomena mediating their perception (Wundt 1896a). Immediate experience comprises connected processes, whereby every process has an objective content but is, at the same time, also a subjective process. Inner experience, Wundt highlighted, is not a special part of experience but rather constitutes the entirety of all immediate experience; thus, inner and outer experience do not constitute separate channels of information as often assumed (Uher 2016a). That is, psychology deals with the entire experience in its immediate subjective reality. The inherent relation to the perceiving and experiencing subject—subject reference—is therefore a fundamental category in psychology. Subjects are feeling and thinking beings capable of intentional action who pursue purposes and values. This entails agency, volition, value orientation and teleology. As a consequence, Wundt highlighted, research on these phenomena can determine only law-like generalisations that allow for exceptions and singularities (Fahrenberg 2019). Given this, it is meaningless to use theories-to-laws ratios as indicators of scientificity (e.g., in Simonton 2015; Zagaria et al. 2020).
Constructs: Concepts in Science AND Everyday Psychology
The processual and transient nature of immediate experience (and many behaviours) imposes further challenges because, of processual entities, only a part exists at any moment (Whitehead 1929). Experiential phenomena can therefore be conceived only through generalisation and abstraction from their occurrences over time, leading to concepts, beliefs and knowledge about them, which are psychical phenomena in themselves as well but different from those they are about (reflected in the terms experiencing versus experience; Erleben versus Erfahrung; Uher 2015b, 2016a). Abstract concepts, because they are theoretically constructed, are called constructs (Kelly 1963). All humans implicitly develop constructs (through abduction, see below) to describe and explain regularities they observe in themselves and their world. They use constructs to anticipate the unknown future and to choose among alterative actions and responses (Kelly 1963; Valsiner 2012).
Constructs about experiencing, experience and behaviour form important parts of our everyday knowledge and language. This entails intricacies because psychologists cannot simply put this everyday psychology aside for doing their science, even more so as they are studying the phenomena that are at the centre of everyday knowledge and largely accessible only through (everyday) language. Therefore, psychologists cannot invent scientific terms and concepts that are completely unrelated to those of everyday psychology as natural scientists can do (Uher 2015b). But this also entails that, to first delineate their study phenomena, psychologists need not elaborate scientific definitions because everyday psychology already provides some terms, implicit concepts and understanding—even if these are ambiguous, discordant, circular, overlapping, context-dependent and biased. This may explain the proliferation of terms and concepts and the lack of clear definitions of key phenomena in scientific psychology.
Constructs and language-based methods entail further challenges. The construal of constructs allowed scientists to turn abstract ideas into entities, thereby making them conceptually accessible to empirical study. But this entification misguides psychologists to overlook their constructed nature (Slaney and Garcia 2015) by ascribing to constructs an ontological status (e.g., ‘traits’ as psychophysical mechanisms; Uher 2013). Because explorations of many psychological study phenomena are intimately bound to language, psychologists must differentiate their study phenomena from the terms, concepts and methods used to explore them, as indicated by the terms psychical versus psychological (from Greek -λογία, -logia for body of knowledge)—differentiations not commonly made in the English-language publications dominating in contemporary psychology (Lewin 1936; Uher 2016a).
Psychology’s Exceptional Position Among the Sciences and Philosophy
The concepts of mediate and immediate experience illuminate psychology’s special interrelations with the other sciences and philosophy. Wundt conceived the natural sciences (Naturwissenschaften; e.g., physics, physiology) as auxiliary to psychology and psychology, in turn, as supplementary to the natural sciences “in the sense that only together they are able to exhaust the empirical knowledge accessible to us“ (Fahrenberg 2019; Wundt 1896b, p. 102). By exploring the universal forms of immediate experience and the regularities of their connections, psychology is also the foundation of the intellectual sciences (Geisteswissenschaften, commonly (mis)translated as humanities; e.g., philology, linguistics, law), which explore the actions and effects emerging from humans’ immediate experiences (Fahrenberg 2019). Psychology also provides foundations for the cultural and social sciences (Kultur- und Sozialwissenschaften; e.g., sociology; anthropology), which explore the products and processes emerging from social and societal interactions among experiencing subjects who are thinking and intentional agents pursuing values, aims and purposes. Moreover, because psychology considers the subjective and the objective as the two fundamental conditions underlying theoretical reflection and practical action and seeks to determine their interrelations, Wundt regarded psychology also a preparatory empirical science for philosophy (especially epistemology and ethics; Fahrenberg 2019).
Psychology’s exceptional position at the intersection with diverse sciences and with philosophy is reflected in the extremely heterogeneous study phenomena explored in its diverse sub-disciplines, covering all areas of human life. Some examples are individuals’ sensations and perceptions of physical phenomena (e.g., psychophysics, environmental psychology, engineering psychology), biological and pathological phenomena associated with experience and behaviour (e.g., biopsychology, neuropsychology, clinical psychology), individuals’ experience and behaviour in relation to others and in society (e.g., social psychology, personality psychology, cultural psychology, psycholinguistics, economic psychology), as well as in different periods and domains of life (e.g., developmental psychology, educational psychology, occupational psychology). No other science explores such a diversity of study phenomena. Their exploration requires a plurality of epistemologies, methodologies and methods, which include experimental and technology-based investigations (e.g., neuro-imaging, electromyography, life-logging, video-analyses), interpretive and social-science investigations (e.g., of texts, narratives, multi-media) as well as investigations involving self-report and self-observation (e.g., interviews, questionnaires, guided introquestion).
All this shows that psychology cannot be a unitary science. Adequate explorations of so many different kinds of phenomena and their interrelations with the most elusive of all—immediate experience—inherently require a plurality of epistemologies, paradigms, theories, methodologies and methods that complement those developed for the natural sciences, which are needed as well. Their systematic integration within just one discipline, made necessary by these phenomena’s joint emergence in the single individual as the basic unit of analysis, makes psychology in fact the hardest science of all.
Idiographic and Nomothetic Strategies of Knowledge Generation
Immediate experience, given its subjective, processual, context-dependent, and thus ever-changing nature, is always unique and unprecedented. Exploring such particulars inherently requires idiographic strategies, in which local phenomena of single cases are modelled in their dynamic contexts to create generalised knowledge from them through abduction. In abduction, scientists infer from observations of surprising facts backwards to a possible theory that, if it were true, could explain the facts observed (Peirce 1901; CP 7.218). Abduction leads to the creation of new general knowledge, in which theory and data are circularly connected in an open-ended cycle, allowing to further generalise, extend and differentiate the new knowledge created. By generalising from what was once and at another time as well, idiographic approaches form the basis of nomothetic approaches, which are aimed at identifying generalities common to all particulars of a class and at deriving theories or laws to account for these generalities. This Wundtian approach to nomothetic research, because it is case-by-case based, allows to create generalised knowledge about psychical processes and functioning, thus building a bridge between the individual and theory development (Lamiell 2003; Robinson 2011; Salvatore and Valsiner 2010).
But beliefs in the superiority of natural-science principles misled many psychologists to interpret nomothetic strategies solely in terms of the Galtonian methodology, in which many cases are aggregated and statistically analysed on the sample-level. This limits research to group-level hypothesis testing and theory development to inductive generalisation, which are uninformative about single cases and cannot reveal what is, indeed, common to all (Lamiell 2003; Robinson 2011). This entails numerous fallacies, such as the widespread belief between-individual structures would be identical to and even reflect within-individual structures (Molenaar 2004; Uher 2015d). Galtonian nomothetic methodology has turned much of today’s psychology into a science exploring populations rather than individuals. That is, blind adherence to natural-science principles has not advanced but, instead, substantially impeded the development of psychology as a science.