William Hasker on Causal Closure and an Evolutionary Argument Against Epiphenomenalism

From here

This review has not examined in detail the various arguments presented; this is precluded by space limitations and by the extent and variety of the material. There is however one argument for which an exception needs to be made. The argument is especially prominent in the essays by Wilson, Angel, and Papineau in Part II, but it is present implicitly or explicitly in many other places. It may be stated as follows:

(1) Nothing that goes on in the brain violates the predictions of physical science.

(2) If there were an immaterial soul affecting the brain this would lead to a violation of physical formulas. Therefore,

(3) There is no non-physical soul that might survive bodily death.

Premise (1) is a consequence of the causal closure of the physical domain: any physical event that has a cause has a physical cause. Or as Angel puts it, “no natural change violates a prediction (or outcome) in physical formulas” (378). Granted this, the rest of the argument is plausible. If this argu­ment is conceded, it gives anti-survivalists most of what they want in a single stroke. To be sure, there are some materialist views of the resurrection that may be consistent with the soundness of (1)-(3). These views would not, however, qualify as among the more plausible and attrac­tive versions of belief in an afterlife. This argument, then, needs to be addressed.

The first point to be made is that, in spite of frequent assertions to the contrary, premise (1) is not known to be true. What is in question is whether an immaterial mind may be exerting a causal influence on what happens in the brain at a micro-level. Influence on this scale is far below the limits of our present capacity to detect. Furthermore, we have only the vaguest notion of what it is we would be trying to detect because we know little about how the brain actually works at this level. I am tempted to say that we don’t know the “machine code” for the brain, but this understates the case. We don’t even know how the basic hard­ware (rather, wetware) functions with regard to giving rise to particular kinds of conscious experience. We don’t know, in spite of many proposals, the neural correlate of consciousness, the minimum neural functioning that is required for any kind of conscious experience to occur. We are roughly in the position of a member of a primitive society who, confronted with a transistor radio, reasons that since there is no human being speaking in the vicinity, the radio must be speaking to him on its own. He simply lacks the equipment that would be required to detect the electromagnetic waves that are carrying the signal to the radio, as well as the knowledge to appreciate their significance. Under these circumstances, the claim that we have experimental verification of premise (1) can’t be made out. One might, to be sure, affirm (1) as a plausible extrapolation from the scientific knowledge we do have, in the light of one’s own overall (probably naturalistic) worldview. Understood in this way, however, the argument no longer has any compelling force against mind-body dualism. Furthermore there is an important objection to (1) even taken in this non-dogmatic way.

This leads to the second point: there is strong reason to think that premise (1) is false. Here’s the argument. We humans are able to engage in conscious rational thought, resulting in a reasonably accurate apprehension of the world in which we live. This can be taken as a datum; clearly, anti-survivalists cannot afford to challenge it, relying as they do on scientific knowledge of many different kinds. This datum, however, is a fact which requires explana­tion. There is, furthermore, one particular sort of explanation which will be accepted by most readers of this review, probably including all anti-survivalists. That expla­nation is found in evolutionary epistemology. The basic idea is familiar: the sorts of mental functioning which lead to a generally accurate apprehension of the world lead thereby to behavior which is conducive to survival and reproduction, and so those sorts of mental functioning tend to prevail over others in the course of evolution. This may or may not be the complete explanation for human rational capabilities (I doubt that it is), but it does seem to be an important part of the explanation.

Now, here is the crucial point: If premise (1) is true, that is, if causal closure obtains, then evolutionary epistemology cannot be the explanation for human rationality. The reasoning is simple and compelling. If causal closure is true, then everything that happens in the brain has its complete explanation in prior physical events, no doubt mainly earlier brain-events. But this means that prior mental events play no role in determining the state of a person’s brain — and therefore, they play no role in the organism’s behavior. It follows, furthermore, that mental events and processes are irrelevant to behavior and are thus invisible to natural selection, which can only operate on physical structures and physical behavior. So natural selection cannot select for superior mental processes, nor can it play any role in explaining the effectiveness of the mental processes we actually employ in getting to know the world. This enormously important fact — that we are able to reason about the world and gain know­ledge of it — is left completely unexplained. I predict, furthermore, that within the generally naturalistic framework that is presupposed in this discussion, it will not be possible to find a promising alternative explanation.

It is sometimes thought that this problem can be surmounted by adopting mind-body identity theory. If the physical brain-event is also a mental event, then the mental event is after all causally relevant to behavior, and natural selection can operate to select superior mental processes. This however is a mistake. We have, it is proposed, a single event, which has both physical characteristics and mental characteristics. Notice, however, thatonly the physical characteristics of the event are causally effective. The causal consequences of that event will be those, and only those, that flow from it as determined by physical forces, as recognized by the true laws of physics. The mental characteristics of the event, whatever they may be, have no effect whatever in determining the subsequent behavior. Once again, natural selection is unable either to select for superior mental function or to explain the efficacy of the mental processes we actually employ. We are left completely without any explanation for the fact, if it is a fact, that mental events that lead to evolutionarily successful outcomes generally coincide with those that involve an accurate representation of the world. The general effectiveness of our reasoning processes is still entirely unexplained. I submit that any view of the mind and the self that has this consequence is at a severe disadvantage. The price for accepting premise (1) of the argument is extremely high.


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