Implication: If you're not irrational, then you're not a physicalist.

If my prior argument (that standard forms of determinism imply irrationality) turns out to be sound, there are several further implications. The first one I wish to expound is a clear case of Modus Tollens.
Modus Tollens is a recognizable logical form wherein the necessary condition for the antecedent is denied, proving that the antecedent must be false. Blah Blah Blah.

Let me put it this way: Being a duck implies being a bird, so if you find out you ain't a bird, guess what? You ain't a duck. In this case being a bird is a necessary condition for being a duck. If you don't meet that criterion, your duck-ness just took a serious hit.

Now leaving such a "foul" analogy behind, allow me to apply this form to the case at hand.

Physicalism is more or less the view that the physical world (governed by the principles of chemistry and physics) exhausts reality. All there is in the universe can be accounted for by the so-called "hard" sciences. We, as human persons, are interesting and complex bundles of physio-chemical processes, but things like a soul or a conscience or an immaterial mind are (at most) just conventional ways of labeling what is ultimately part of the natural world.

You can see, no doubt, that physicalism implies determinism. If everything is physical (or material)* and is therefore governed by the immutable laws of chemistry and physics, then there is no room for a human will to deviate from the natural order. One's "choices" then are simply a part of the closed system of material causes and effects. They are not free in any meaningful sense of the word, for they follow necessarily from previous events, conditions, and circumstances.

So here's the simplified argument:

1. Physicalism implies determinism
2. Determinism implies irrationality.
3. Therefore, Physicalism implies irrationality.
4. However, I am not irrational.
Therefore, Physicalism is false.

Modus Tollens baby.

I leave you now with further questions. If there is more to reality than the physical universe, then what is it? If we do have rationality, conscience, or immaterial souls, how do we make sense of them? Whence did they arise? No doubt, some of you already have some great answers.



*For my purposes materialism and physicalism can be regarded as synonymous.