Hempel’s Dilemma

It is often expected that a position be defined before it be rejected. In the case of physicalism, however, a reason for rejecting the position is the fact that it cannot be properly defined. This ambiguity in the meaning of “physicalism” is brought out through what is known as Hempel’s Dilemma, named after its formulation by philosopher Carl G. Hempel,[1] though it was in fact formulated earlier by Herbert Feigl.[2] The dilemma: it seems that the meaning of physicalism can be grasped through either of two horns. The first horn is exclusive belief in the phenomena of current physics, such as matter-energy, space-time, the fundamental interactions, and so on. The problem herewith is that such a belief is highly unlikely to be true. This is in part because we can witness the constant change of physics through history, realizing that our current state of understanding is but a moment within this history and thus, by pessimistic induction,[3] we realize that physics is likely to continue changing. Secondly, as is well known, the current state of physics cannot be final due, in particular, to the inconsistency between general relativity and quantum mechanics. Thirdly, as will be seen below, the role of the mind in current physics is undetermined.

Thus a self-proclaimed physicalist might therefore instead embrace the second horn of the dilemma: belief in the phenomena of a future, ideal physics. Yet there are two chief problems with this alternative. Firstly, how could one believe in physicalism if one did not know what that was? One may almost as well profess one’s adamant belief in drallewertism. Secondly, it may turn out that a future physics would include mentality amongst its fundamental elements. But because physicalism, as material monism, is as such opposed to dualism (one where mind and matter are equally fundamental), such a possibility would seem to contradict the current understanding of physicalism. As a result of this implication, many self-proclaimed physicalists add a “no-fundamental-mentality” condition to the meaning of physicalism to preclude such a possibility.[4] However, one cannot determine the future direction of physics, thus physicalism, by advancing ad hoc exclusionary clauses to suit one’s current preferences. It may well be that a future physics will be contrary to “physicalism,” as understood in such current exclusionary terms.

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This article first appeared in issue 2 of The Side View Journal. Purchase your own copy here. 

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Where does Hempel’s Dilemma leave us?

It seems one cannot accept physicalism according to the first horn, nor can one accept it according to the second. This disposes us to a current position of agnosticism towards physicalism: it is not rational to place one’s belief in a position that is either wrong or unknown.

Irreducible Mentality

Current physical properties cannot describe nor explain mentality, therefore reality must be more than that which such physicalism presents. I cannot describe mental states such as hunger, despair, pain, or curiosity using physical properties alone—it would be an unintelligible category mistake to describe my hunger as comprised of a certain mass, gravity, volume, charge, and shape. But can I not say that my mental states are identical to their physical correlates, and thus describe them using such physicalist terms?

There are a host of logical reservations against such an identification. One can be called the multiple realization dilemma: if hunger (H) were identical to its human physical correlates (HPC), it would either imply that only humans could feel hunger (an implausible, unprovable position)—or it would imply that hunger was identical to both human physical correlates and to, say, shark physical correlates (SPC); but this would in turn imply that the human and shark physical correlates were identical (if H = HPC, and if H = SPC, then HPC = SPC), which is absurd.[5] So it seems illogical to posit that a mental state is the same thing as its physical correlate.[6] Thus one cannot describe or explain mentality in such physicalist terms alone.

As a result, physicalists have reconceptualized the mind-matter relation as one of emergence: that the mind emerges from certain brain activity. The two main problems associated with this approach are, firstly, that the specific nature of such an emergence is unknown: there are no known “bridge-laws” (or, no “transordinal nomology”) between the physical and the mental (they are certainly not known laws of physics). That the movement of matter can manifest mentality is the magical miracle that makes materialism a sect not a science. Secondly, it is unknown how the mentality that emerges from matter could in its turn have any power upon that matter—as most emergentists would demand so to avoid epiphenomenalism (the view that mentality is a useless aftereffect of cerebral machinations).

Of course one could bite the bullet and accept epiphenomenalism, but this arguably presents more problems than it solves. Furthermore, certain other physicalists are loathe to even call emergentism a type of physicalism because it seems ultimately to assert the emergence of a mental substance into the physical realm.[7] An extreme, yet minor, response from physicalists is to deny the existence of mentality altogether. But this position soon implodes, for reasons such as believing that there are no beliefs with the satisfaction that there are no satisfactions.

Most thinkers accept the reality of both of the physical and mental correlates of consciousness, but the relation between the two is not, then, explained in physicalist terms. Even a completed mapping of the neural correlates of consciousness would not solve the question as to the nature of the correlation—the correlation presents the question not the answer. Thus we have little reason to accept a physicalism that cannot account for the most pressing aspect of our realities: consciousness. As even Ivan Pavlov acknowledged, “only one thing in life is of actual interest for us—our psychical experience.”[8] Again, this does not in itself mean that we should thereby endorse any particular non-physicalist ideology, such as dualism or idealism. Rather, this simply means that it is more plausible to reject physicalism, leaving one as an ontic agnostic, knowingly unknowing.

The Evolutionary Argument against Physicalism

The physicalism of today accepts four fundamental interactions: gravity, electromagnetism, and the strong and weak nuclear forces. It does not accept mental force. The ultimate, counter-intuitive and thus mostly unwanted implication of this is epiphenomenalism: that mentality is completely useless, like the steam from a locomotive engine.[9] As well as the British idealist F. H. Bradley,[10] the influential philosopher of science Karl Popper[11] argues that such a belief is anti-evolutionary because were mentality impotent it would not have evolved. To suggest that one’s beliefs, desires, ambitions, calculations, perceptions, investigations, subconscious drives, emotions, plans, rationalizations, have absolutely no effect upon one’s body and thus upon the world is not only anathema to common sense, to the science of psychology, and to the power of reason, but is also a mockery of evolutionary theory (not to mention the Eleatic Principle).[12]

Not only does mentality exist in humans, but also presumably in the myriad other species of this world. For mentality to evolve and to maintain itself therein, without any purpose or power, runs against our notions of evolution, of selection. For instance, have we not evolved our intelligence, our reasoning powers? Did they not aid our survival and development? Very few will deny this premise, but a physicalist will deny mental force, mental causation: the power of the mind, as it is not a known fundamental force. Thus physicalism conflicts with evolutionary theory. To try to overcome this by identifying the mind with the physical will not work because: (1) psychoneural identity theory has failed, and (2) if mental powers are actually physical powers, one thereby returns to the predicament of having to explain why mentality exists if it has no powers of its own. The final outcome is that if one accepts evolution one must deny physicalism.

The Universal Cracking of Causal Closure

Most physicalists accept the causal closure principle: “If a physical event has a cause at t, then it has a physical cause at t.”[13] This does allow, per se, for the possibility of uncaused events, and it does allow for the existence of other non-physical realms, so long as they do not affect the physical realm. What it does not allow for is mental causation upon the physical, which in turn implies epiphenomenalism, which leads to evolutionary problems, as discussed in the previous section. But there is another problem to which this perspective leads: that objective truths cannot have any causal influence upon the physical world.

The philosopher David Papineau writes, “I think that physicalism is best formulated, not as the claim that everything is physical, but as the significantly weaker claim that everything that interacts causally with the physical world is physical. This leaves it open that there may be noncausal realms of reality that are not physically constituted, such as the realm of moral worth, or of beauty, or of mathematical objects.”[14] More than two decades before this writing, Karl Popper had already identified the problem with such a view: “The standards of logic are not physical properties . . . but they are useful for survival; which means they have causal effects in the physical world.”[15]

If one accepts, as even Papineau suggests, that there exists what the logician Frege called “the third realm”[16] (beyond physicality and mentality) of objective truths—such as the truth of modus ponens, the properties of Pi, the Pythagorean theorem, or the Form of Beauty—truths that exist whether or not they are discovered, meaning that they are in essence neither mental nor physical (as there can be no neural correlates of non-existent mental events), then it implies that their existence has an effect upon the physical through their discovery. For example, the discovery of the golden ratio had an effect upon the bodies of its discoverers in terms of their expression of it, and subsequently upon mathematics, aesthetics, architecture, and upon me in writing this essay. Thus the existence of such universal truths implies the falsity of one of physicalism’s key tenets: the causal closure of the physical. Universals crack open the causal closure principle of physicalism, which is to say they crack open physicalism itself.

Of course, a physicalist could deny the existence of such universals, such objective truths. But in doing so, he would destroy the underlying assumptions of his position and thus succumb to inconsistency regardless. If physicalism considers itself to be a logical position, it must maintain the underlying truths of the laws of logic, such as the law of non-contradiction, formal fallacies, and so on. But these laws are not the laws of physics, which as such can be established through empirical observation or through modelling. Thus emerges another predicament for physicalism: the dilemma of logical objectivity. On the one side, if the laws of logic are to be considered objective—that is, they are true for all—then they must exist in a non-temporal, non-physical third realm that has causal influence upon the physical, thereby annulling the causal closure principle and, in turn, physicalism. On the other side, if the laws of logic are considered to be not objective, then physicalism cannot claim to be objectively logical. Either way, physicalism falters.

A World of Possibility

These are but four brief arguments for being sceptical of physicalism, for withholding assent to this belief system. These arguments do not thereby advance any other system of belief but merely leave one lost in a field of ignorance which, to apply a positive spin, opens one up to a world of possibility.

 

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[1] See Carl G. Hempel, “Reduction: Ontological and Linguistic Facets,” in Philosophy, Science, and Method: Essays in Honor of Ernest Nagel, eds. P. Suppes, S. Morgenbesser, and M. White (New York: St. Martins, 1969), 179–199 and Carl G. Hempel, “Comments on Goodman’s Ways of Worldmaking,” Synthese, XLV (1980), 193–199.

[2] See Herbert Feigl’s 1963 essay, “Physicalism, Unity of Science and the Foundations of Psychology,” as cited in Inquiries and Provocations: Selected Writings 1929–1974, eds. Herbert Feigl and Robert S. Cohen (Dordrecht: D. Reidel Publishing Company, 1981), 316.

[3] See Larry Laudan, “A Confutation of Convergent Realism,” Philosophy of Science, 48:1 (1981), 19–49.

[4] For instance, see David Papineau, “The Rise of Physicalism,” in Physicalism and Its Discontents, eds. Carl Gillett and Barry Loewer (Cambridge: Cambridge University Press 2001), 3–36.

[5] See Alvin Plantinga, “Evolution, Epiphenomenalism, Reductionism,” Philosophy and Phenomenological Research, LXVIII: 3 (2004), 602–619.

[6] “Physical” here meaning that used in currentism. There may be a deeper identity as yet undiscovered.

[7] See J. J. C. Smart, “Materialism,” The Journal of Philosophy, 60: 22 (1963), 651–662.

[8] Said within his 1904 Nobel Prize acceptance speech. See Ivan Pavlov, Experimental Psychology and Other Essays (New York: Philosophical Library, 1957), 148.

[9] See Thomas Huxley, “On the Hypothesis that Animals are Automata, and Its History,” The Fortnightly Review, 16 (1874), 555–580.

[10] Francis H. Bradley, “On the Supposed Uselessness of the Soul,” Mind, 4: 14 (1895), 176–179.

[11] Karl Popper and John Eccles, The Self and Its Brain (London: Springer International, 1977), 72–75.

[12] The Eleatic Principle: The definition of being is simply power. Or: “A thing really is if it has any capacity at all, either by nature to do something to something else or to have even the smallest thing done to it by even the most trivial thing, even if it only happens once. I’ll take it as a definition that those which are amount to nothing other than capacity.” Plato, Sophist, 247d.

[13] Jaegwon Kim, Physicalism, or Something Near Enough (Princeton: Princeton University Press, 2005), 15.

[14] Papineau, “The Rise of Physicalism,” 11.

[15] Popper and Eccles, The Self and Its Brain, 79.

[16] Gottlob Frege, “The Thought: A Logical Enquiry,” Mind, 65: 259 (1918–19/1956), 289–311.