Karl Popper, Subjective Conscious Experiences and The Methods of Psychology


In this paper I explore Karl Popper’s interpretation of the Gestalt Switch as providing evidence for subjective conscious experiences yielding the conclusion that phenomenological evidence for subjective conscious experiences is at least possible and that evidence, both of the phenomenological and psychological sort, will challenge the reductive route to consciousness. I shall argue that this evidence meets strict epistemologies—most notably the epistemology and criteria set by the behaviorist route to consciousness—and has methodological implications for the field of psychology for exploring mental phenomena and consciousness generally. I begin by exploring epistemological and methodological questions consciousness and subjective conscious experiences raises, and then turn to ways in which they can be approached. I then draw attention to two epistemological issues and one phenomenological with the behaviorist route, and proceed to outline Karl Popper and Sir John Eccles’ work The Self and Its Brain (1977/1985). As such, I make explicit his interpretation of the Gestalt Switch and then explore epistemological and phenomenological issues regarding subjective conscious experiences and its implications for a reductive theory of consciousness. In the end, I suggest that psychological methods for providing evidence for subjective conscious experiences has implications for mental phenomena and consciousness generally and, in the end, I suggest that inasmuch as the anti-reductive route to consciousness is taken, there exist potential psychological, philosophical and theological implications.


Consciousness raises methodological, epistemological and explanatory problems in psychology and philosophy of mind. How to interpret mental phenomena—consciousness particularly—has been of focal importance to both psychologists and philosophers of mind. Whether or not it is justifiable or warranted to explain, reduce or eliminate consciousness from the contemporary data is an issue of great psychological importance. Thus, I will focus on the psychological evidence for subjective conscious experiences by the 20th century philosopher of science Karl R. Popper (1977/1985) and then shift the discussion to consider further epistemological and phenomenological problems for a reductive theory of consciousness. So, in this paper, I shall argue that Karl Popper’s interpretation of the Gestalt Switch as providing evidence for the existence of subjective conscious experiences suggests, in conjunction with phenomenological and epistemological considerations, that the anti-reductive route to consciousness will be most conducive to constructing a fundamental theory (or explanation) of consciousness. This has methodological implications for approaches to mental phenomena generally and so the conclusion of this paper leaves an open research project for further work on psychological evidence for subjective conscious states.

An important two-fold question is raised by the existence of consciousness. First, how do we know that subjective conscious experiences exist?[1] If this question yields a positive answer, then what methods are there to detect it? So, before any analysis of consciousness these preliminary, foundational questions merit attention. To answer the first question requires some sort of evidence. Here, there seems to be three routes. The first route I shall call the ‘behaviorist route’, the second I shall denote as the ‘reductive route’ and the third the ‘anti-reductive route.’[2] The ‘behaviorist route’ denotes two theses, namely, that 1) there can be no interior evidence for consciousness i.e., appeals to introspection and therefore 2) what constitutes evidence for subjective conscious experiences will have to be such that they are inferred and explained simply by virtue of a person’s behavior. On the other hand, the ‘reductive route’ is the view that mental phenomena or consciousness (or subjective conscious experiences) is reducible to matter. In other words, the linguistic terms in psychology of a human person as having i.e., thoughts, feelings, desires et cetera, are all essentially reducible to a person’s material constituents (or the conjunction of material constituents i.e., a brain state); what has been called “personal explanation” becomes reducible to scientific terminology (Stainton & Brooks, 2000). Contrarily, the ‘anti-reductive route’ to subjective conscious experiences 1) admits of phenomenological or interior evidence of mental phenomena insofar as the person in question’s testimony is reliable and such that the phenomenal character of experience (qualia) is presumed to also be reliable; and, the anti-reductive route argues that 2) subjective conscious experiences, mental phenomena and the like are not reducible to anything material (although it might be correlated with it in multiple and interesting ways) (Nagel, 2012). Before moving on to discuss the psychological evidence for consciousness, I have two comments to make concerning the behaviorist route. But, first I shall comment on the behaviorist route and present psychological evidence for subjective conscious experiences.

There are many epistemological issues with behaviorist route. With respect to my first comment, I would like to raise two epistemological problems and one phenomenological for the behaviorist route. First, there is a hidden presupposition of verificationism (Ayers, 1946/1952) in the behaviorist route since a principle problem with ‘introspective evidence’ is that none of the testimony can be verified. Whether or not this is a faulty epistemology (and I do believe it is faulty), it is a presupposition which dominated in 20th century logical positivism, but is now rendered restrictive and self-refuting (Craig & Moreland, 2003, pp. 154-155). Secondly, there exists a particular variety of scientism that underlies this view. Scientism is the view which states that knowledge, if it is to be counted as knowledge, must be attained from the hard sciences i.e., physics, chemistry and biology; any claim to knowledge outside the hard sciences cannot be counted as knowledge. Like verificationism, scientism fell into the same self-refuting category (Craig & Moreland, 2003, pp. 346-348). So, epistemologically the behaviorist route leads to a self-refuting epistemology. To turn to the phenomenological objection to the behaviorist route, I shall employ the argument that Nagel (2012) adopts. In lodging a critique against contemporary attempts to incorporate consciousness into a naturalistic framework in conjunction with the epistemology of scientism, Nagel attacks the behaviorist approach to mental phenomena as such. He claims that the behaviorist route (or anything close to it) are inadequate inasmuch as “they leave out something essential that lies beyond the externally observable grounds for attributing mental states to others, namely, the aspect of mental phenomena that is evident from the first-person, inner point of view of the conscious subject.” (Nagel, 2012, p. 38). The introspective or phenomenological life of a person is ineliminable from analysis of the mental such that a theory which eliminates it leaves a gap in our understanding of the mental. So, Nagel (2012) suggests, although the behaviorist route can account for the physical, external manifestations of the mental, it “leaves out the inner mental state itself.” (Nagel, 2012, p. 38). The second comment I would like to make regarding the behaviorist route is a deconstructive one with a positive counterpart. Although the behaviorist route has epistemological and phenomenological issues, Karl Popper’s interpretation of the Gestalt Switch provides evidence for subjective conscious experiences while simultaneously meeting the standards of the behaviorist route.

Karl Popper and Sir John Eccles’ work (1977) is a rigorous defense of interactionism, that is, the view according to which the self is a real and objective feature of reality and it is in conjunction, and interaction with, a physical body.[3] Popper, in setting out his project of establishing interactionism, begins with an ontological framework, that is, a framework positing what does and does not exist. He distinguishes three ‘worlds’ (W1, W2, W3) and characterizes them as follows (Popper & Eccles, 1977/1985, p.16):


World 3                                             (6) Works of Art and of Science (including technology)

(the products of the human mind) (5) Human Language. Theories of Self and of Death

World 2                                                 (4) Consciousness of Self an of Death

(the world of subjective experiences) (3) Sentience (Animal Consciousness)

World 1                                                 (2) Living Organisms

(the world of physical objects)      (1) The Heavier Elements; Liquids and Crystals

(0) Hydrogen and Helium



So, the existence of consciousness falls into categories (3) and (4) and are therefore part of W2. For Popper, as it is stated above, W2 is the world of subjective experiences; further, while the legitimacy of such an ontological framework is beyond the scope of this paper, the table above will help to contextualize and conceptualize where subjective conscious experiences lie. Popper then moves on to criticize materialism and its varieties—beginning with, among other characterizations, what he calls ‘Radial Behaviorism.’ The ‘behaviorist route’ and the ‘Radical Behaviorism’ seem to me to be synonymous and thus I will not make technical distinctions between Popper’s characterization and my own view. (If our conceptions of behaviorism are not synonymous, Poppers argument still poses challenges to the behaviorist route—the technical distinction is at best irrelevant to my argument). Popper’s argument hinges on an important principle, namely, that “we can establish empirically, by behaviorist methods, that subjective, conscious experience exists.” (Popper & Eccles, 1977/1985, p. 66). The point is not that the behaviorist has to commit herself to the reliability of introspection as a source of knowledge concerning mental states; rather, the threshold of the argument is that the reductive route to consciousness is unavoidable—even on a restrictive epistemology i.e., behaviorist route.[4] Popper makes explicit the Gestalt Switch he has in mind (Popper & Eccles, 1977/1985, p.65)[5]:  gestalt

The purpose of this American Indian/Eskimo Gestalt Switch example is, Popper suggests, that “we can voluntarily and actively build up the profile of the Indian by looking at his nose, mouth, and chin, and then proceeding to his eye. As to the Eskimo, we can start to build him up from his right boot” and therefore “we can formulate experimental questions about these activities which lead to intersubjectively repeatable answers.” (Popper & Eccles, 1977/1985, p.65). The behaviorist route to consciousness, in requiring a non-introspective approach to subjective conscious experiences, is thus accommodated via the psychological method. While the Gestalt Switch example provides one example of “intersubjectively testable experiments” yielding the conclusion that “men have conscious experiences”, it follows that the reduction of mental phenomena to the evidence behavior provides is, as far as the psychological method is concerned, at best unnecessary (Popper & Eccles, 1977/1985, pp. 65-66).[6] Interpreting the Gestalt Switch in this way has two essential implications.

If Popper’s interpretation of the Gestalt Switch is correct, I shall argue that what follows is that subjective conscious experiences are not eliminable and that a future project for psychology will be applying different methods to provide evidence for subjective conscious experiences.[7] With respect to eliminability, subjective conscious experiences can only be eliminated if they do not exist; any pragmatic approach, I suggest, will be at best ad hoc. For instance, if some mental state M is said to exist which explains i.e., the sensation of blue, then M provides an explanation for the sensation of blue. To eliminate M (on any grounds other than evidential grounds) and suggest an alternative theory for the sensation of blue, say M*, is to simply deny M and not show ontologically that M does not exist. M* is ad hoc inasmuch as it begs the question against M and purports to show, based on i.e., theoretical virtues, that M does not exist. Analogously, since evidence for subjective conscious experience is suggested from the Gestalt Switch, eliminating subjective conscious experiences without justification seems to necessitate an ad hoc argument and consequently deny the best explanation of the Gestalt Switch. With respect to the latter contention, that there exists a further research project for psychology to provide other possible and alternative methods by which evidence can be given in support of the existence of subjective conscious experiences, I think there exists important implications of subjective conscious experiences existing—I shall name two.

First, subjective conscious experiences are phenomenologically known; in one’s subjectivity, it is a simple experiential truth that subjective conscious experiences occur and therefore any evidence for this proposition will suggest that our phenomenological intuitions are valid. Secondly, if subjective conscious experiences exist, the reductive route to consciousness is further constrained; while the reductionist programme has as its goal reducing consciousness to physical constituents which is incompatible with our moral intuitions i.e., regarding persons as “irreplaceable” with the counterpart implication that “in being irreplaceable [persons] are clearly very different from machines.” (Popper & Eccles, 1977/1985, p. 3). While this claim is controversial, it seems that whether or not this is true, this provides minimally pragmatic motivation for further work in psychology and also motivation for consistency; a consistent philosophical anthropology must not entail all aspects of a person inasmuch as these aspects are ineliminable inasmuch as consistency is a necessary condition for modeling persons. I suggest that psychology, with further work, will make accessible more methods by which evidence can be provided for subjective conscious experiences.[8]

Given that there exists psychological evidence for subjective conscious experiences, it is an interesting question whether or not there could exist phenomenological evidence for subjective conscious experiences. It seems that the evidential reasons for granting the ontology of subjective conscious experiences leaves open the mere possibility of such phenomenological evidence. However, it is my speculation and conjecture that any argument from the phenomenology of a person will rely on an epistemology, that is, considerations relevant to the theory of knowledge. For instance, Alvin Plantinga (2011) argues that properly basic beliefs are such that in the absence of some defeater i.e., a reason to deny the belief in question, one is rational in affirming the belief. So, under this rubric (which I am laying out here broadly) one should take their experience of subjective conscious experiences as phenomenologically valid (inasmuch as it is, according to Plantinga, epistemologically valid).[9] So, if subjective conscious experiences are posited justifiably both evidentially and epistemologically (derivative from a person’s phenomenology), it seems to follow that the reductive route to consciousness is severely challenged inasmuch as it will have to account for subjective conscious experiences known both by one’s phenomenology and the evidence of psychology; this leaves open a further research programme for psychology in detecting other methods of providing evidence for subjective conscious experiences.

In this brief paper, I hope that I have shown how psychological methods i.e., the Gestalt Switch, makes probable the existence of subjective conscious experiences even in conjunction with a behaviorist criteria for assessing mental phenomena. There exist vast areas in this paper I have not explored, most notably the problem of the potential reducibility and eliminability of consciousness to physical constituents and the problem of prior probabilities with regard to ontological frameworks prohibiting—or making vastly improbable—the existence of consciousness. While my intuitions suggest none of these reductive models are accurate,[10] a research project for future psychological work on the problem of consciousness—and subjective conscious experiences more generally—is available here; the task is to use alternative psychological methods to provide evidence for subjective conscious experiences which, I suggest, will appeal both to strict epistemologies i.e., behaviorist, as well as challenge the reductive route to consciousness. While the aforementioned Gestalt Switch evidence meets the behaviorist criteria, it is worth noting that evidence, notably phenomenological evidence, provides sufficient evidence for subjective conscious experiences; however, it is with further work in psychology that, even under strict or narrow epistemologies, subjective conscious experiences can be shown to exist. Other important questions will arise from further work and if, as I suggest, the anti-reductive route to consciousness is taken, the existence of consciousness and subjective conscious experiences will possibly yield conclusions having philosophical, psychological and theological implications.[11]


Works Cited

Ayer, A.J. (1946). Language, truth and logic. New York: Dover Publications. (Original work published 1952).

Gregory, R.L., & Gombrich, E.H. (1973). Illusion in nature and art. Duckworth: London.

Moreland, J.P. (2008). Consciousness and the existence of God. New York: Routledge.

Moreland, J.P., & Craig, W.L. (2003). Philosophical foundations for a Christian worldview. Downers Grove, Illinois: Intervarsity Press.

Nagel, Thomas. (2012). Mind and cosmos: Why the materialist neo-darwinian conception of human nature is almost certainly false. New York: Oxford University Press.

Plantinga, Alvin. (2011). Where the conflict really lies: Science, religion and naturalism. New York: Oxford University Press.

Popper, Karl., & Eccles, J. C. (1985). The self and its brain. New York: Springer International. (Original work published in 1977).

Rehman, R. Theistic explanations of the ontology of consciousness. Retrieved on January 22, 2016 from https://rashadrehmanca.wordpress.com/

Stainton, Robert., & Brooks, A. Knowledge and mind: A philosophical introduction. Cambridge, Massachusetts and London, England: MIT Press.

Swinburne, Richard. (2013). Mind, brain and free will. Oxford: Oxford University Press.

[1] Throughout the essay I shall use the term ‘consciousness’ to be roughly synonymous with ‘subjective conscious experiences’ in that experiences of the ‘conscious’ sort entail a possessor (at least in the case of human persons) of the conscious state; conscious states, then, is particular to a person subjectively.

[2] I am not arguing against the whole or entirety of behaviorism; rather, I am attacking one of its central theses, namely, that mental phenomena can be accounted for simply by analyzing a person’s behavior.

[3] I will hereafter refer to Popper only for two reasons. First, I am only familiar (and hopefully competent) with Poppers section in the book and not Eccles. Secondly, I am only discussing Poppers interpretation of the Gestalt switch—not the overarching project of the book i.e., establish interactionism.

[4] I would like to make two comments here. First, Popper has another argument which, though not relevant to my essential thesis, merits to be stated here. He argues that “Just as in physics we introduce theoretical entities – in order to explain our observation statements… so we can introduce, in psychology, conscious and unconscious mental events and processes, if these are helpful in explaining human behavior” (Popper & Eccles, 1977/1985, p. 62). While it lies beyond the scope of this paper to explore the legitimacy of this argument, I would like to make two brief comments. First, the fundamental question with respect to subjective conscious experiences is the ontology of such experiences—not its explanatory power. Secondly, one of J.P Moreland’s criteria (2008) for assessing the legitimacy of a scientific theory is ontological basicality, that is, how “at home” the postulated entity is in the theory itself. Now, without a Bayesian framework, it is simply not known whether or not conscious and unconscious events are ontologically basic i.e., it is only relative to an ontological framework entailing background information and evidence that the probability of the hypothesis in question can be assessed. So, it seems presumptuous to postulate such an entity pragmatically without justification (or, minimally, an epistemic virtue i.e., ontological basicality, which would bestow on the theory some degree of justification). Secondly, while I have, I hope, shown that psychological methods i.e., the Gestalt Switch has implications for the existence of subjective conscious experiences, whether or not these experiences are reducible to physical constituents (or not) is beyond the scope of this paper.

[5] This photograph of the Gestalt Switch in this paper is the one used by Popper taken from R.L Gregory and E.H Gombrich (1973) which I have retrieved from an online chapter of Popper and Eccles’ work (1977/1985).

[6] As I have explained in an aforementioned footnote, Popper’s approach to subjective conscious experiences generally, that is, subjective conscious experiences are posited inasmuch as they provide theoretical virtues i.e., explanatory power, the legitimacy of this claim—while disputable—seems to hint at an important insight here. It might be, as Popper suggests, that because the behaviorist route is rendered improbable by evidence derived from a particular method of psychology which provides evidence for subjective conscious experiences i.e., the Gestalt Switch, it seems to follow that either 1) subjective conscious experiences are, even under a behaviorist epistemology, justified to posit ontologically or 2) that subjective conscious experiences are ineliminable and will be an indispensable to a fundamental philosophical anthropology (or, one might say, an adequate ‘ontology of the human person’).

[7] An objector might here retort: Why psychological, not scientific investigation? To this, I must simply admit that I am not hopeful regarding approaches to subjective conscious experiences from the scientific method. I am persuaded, rather, that there is a constant correlation between psychological states and physical states (psycho-physical laws); here, at best, science could provide evidence that they are constantly correlated i.e., experiencing a sensation of pain (there is a physical component and a correspondent mental component) but not evidence as psychology could provide i.e., Gestalt Switch. (Whether or not this is an adequate or inadequate stance regarding the scientific method in this area, I shall proceed no further since it is at best irrelevant to my argument in this paper).

[8] Popper does note more ways in which subjective conscious experiences can be shown i.e., optical illusions, conscious patients with brain stimulations via an electrode resulting in re-living particular past experiences, et cetera (Popper & Eccles, 1977/1985, pp. 63-66).

[9] I am using ‘valid’ informally here; I am not denoting the usage by logicians i.e., ‘valid’ def. the truth of the conclusion following from the premises.

[10] I have, in a currently unpublished essay “Theistic Explanations of the Ontology of Consciousness” (2016), argued that the existence of consciousness contributes to raise the probability of the truth of theism. The rough draft of the paper can be accessed at my personal blog (2016). The thesis of the paper suggests that reductive, eliminative, materialist and physicalist models of consciousness do not work (or at any rate are much less probable that the explanation theism provides).

[11] This paper is written from a philosophical perspective. That being said, I am overlooking many contemporary and historical issues in psychology that either I am not competent to answer, am wholly ignorant of and/or space does not allow for. I hope my work here makes probable a particular thesis or, minimally, shed light on subjective conscious experiences from a unified perspective i.e., bringing psychological work into the realm of contemporary analytic philosophy of mind.


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