David Chalmers on Physical Entailment

Word Count: 860

David Chalmers writes:

“The facts about experience cannot be an automatic consequence of any physical account, as it is conceptually coherent that any given process could exist without experience. Experience may arise from the physical, but it is not entailed by the physical.”

One can be rhetorical now and state the following:

Who cares if it is “conceptual coherent that any given process could exist without experience”?

Surely what matters is that whenever we have the sort of physical processes which give rise to experience, then they always do give rise to experience. Still, there may not be a necessary connection between anything physical and experience; and experience may not be a necessary consequence of anything physical. (Of course all this depends on how we interpret these modal terms and what work they're doing.)

More particularly, what work is Chalmers' notion of any x (or P) being “conceptually coherent” doing here? For one, it can be said that Chalmers is a philosopher, not a physicist or a neuroscientist. Thus Chalmers is interested in what is conceptually coherent and what isn't. Though even if Chalmers is thinking purely philosophically (or in terms of “logical possibility”), what philosophical mileage is he getting out of the conceptually coherent logical possibility that no physical process entails experience? What can we extract, philosophically, from that?

Well, we can extract the logical possibility that nothing physical necessarily gives rise to experience. So are we going around in circles here?

Not necessarily.

The bottom line is that Chalmers believes that experience is over and above the physical. To put that another way (as Chalmers does), “experience is not entailed by the physical”. This raises a question:

What is it for something physical to entail experience?

Or more broadly:

What is it for something physical to entail anything?

Isn't entailment a non-ontological notion?

In linguistics, for example, we have the following definition of entailment:

"Linguistic entailments occur when one may draw necessary conclusions from a particular use of a word, phrase or sentence. Entailment phrases are relations between propositions, and are always worded as, 'if A then B,' meaning that if A is true, then B must also be true. Another way of phrasing this is, 'if A is true, then B must necessarily be true.'..."

It's also the case that both semantic and pragmatic entailment are themselves essentially linguistic. However, it's logical entailment that primarily interests Chalmers. Yet here again we have the following definition:

“Logical consequence (also entailment) is a fundamental concept in logic, which describes the relationship between statements that hold true when one statement logically follows from one or more statements. A valid logical argument is one in which the conclusion is entailed by the premises, because the conclusion is the consequence of the premises.”

So why is Chalmers applying entailment to the physical? The only way around this (as far as I can see) is to say that statements (say, premises) about the physical may entail further statements (conclusions) about the physical. However, will that even work? In order to make that work, the statements which do the entailing would need to be taken as true; and the statemental entailments would need to be taken as the necessary consequences of true statements about the physical.

Having said all that, even if the entailing statements were true, how could they entail other statements if both are about the physical? The entailment itself (that is, the relation between entailing statements and entailed statements) would need to be known to be true a priori. However, since they're about the physical, then how can the entailment be known to be true a priori?

What about a posteriori entailment? Take this example:

Here is a sample of water.

That statement entails the following:

Here is a sample of H₂O molecules.

But isn't this because there's a “hidden premise” or indentity statement in that entailment? Namely:

water = H₂O 

So is Chalmers demanding an identity between any physical x and any experience y in order to have his physical entailment? That is, x can only entail y if x and y are one and the same thing. If x and y aren't one and the same thing, then there can be no entailment.

Could there be physical entailment without such identity? Is it the case that any x can entail any y without x and y being one and the same thing? That is, if x is the case, then (necessarily) y must also be the case. Perhaps in the case of the physical and experience, there is no necessity. (As argued by Kripke, etc.) But do we need necessity here? That is, every time there is a physical x (as in brains, etc. being in a certain states), then there will be experience. Is it necessary that there is experience given any physical x? Well, yes and no. If we have a given physical x, then there is always experience. Having said that, even if physical x always comes with experience, it may still not be necessary that this physical x comes along with experience. This leads me to ask, again: What work is the modal word “necessary” doing here?