David Chalmers is well-known for asking this question (or variations based upon it):
“Why should physical processing give rise to a rich inner life at all?”
So let’s be more specific than that and tackle Chalmers’ references to the physical entailment of experience. For example, he 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 in response to that passage and state the following:
In what way does it matter that it is “conceptually coherent that any given process could exist without experience”?
Surely what matters is this:
Whenever we have the sort of physical (or brain) processes which give rise to experience, then they always do give rise to experience.
Indeed how could any “facts about experience” be an “automatic consequence of any physical account”? In this context it’s hard to know what the word “automatic” means.
Alternatively, is Chalmers asking a question which simply can’t be answered (at least not to his satisfaction)?
So it may be true that there’s no necessary connection between anything physical and experience. (Alternatively put: experience may not be a necessary consequence of anything physical.) Of course all this will at least partly depend on how we interpret — or define — the modal terms “necessary” and “may”.
In addition, what work is Chalmers’ notion of any x (or P) being “conceptually coherent” doing here? In reply to that question it can be said that Chalmers is a philosopher, not a physicist or a neuroscientist. Thus Chalmers is interested in what is and what isn’t conceptually coherent. That said, even if Chalmers is thinking purely philosophically (or in terms of logical possibility), we can still ask him what philosophical mileage he’s getting out of the conceptually coherent logical possibility that no physical process entails experience. What can we extract from that?
Well, we can extract the logical possibility that nothing physical necessarily gives rise to experience.
Are we going around in a circle here when the words “necessary”, “automatic”, “possibility” and “conceptually coherent” are used? That is, don’t all of these words constitute a mutually inter-definable “closed circle of terms”?
The bottom line is that Chalmers believes that experience is (in the colloquial) over and above the physical. To put that another way (as Chalmers has just done), “experience is not entailed by the physical”. This raises this question:
What is it for something physical to entail experience?
Or more broadly:
What is it for something physical to entail anything?
That question is asked because it can be said that entailment is a non-physical notion.
In linguistics, for example, we have the following definition of the word “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 (or logical consequence) 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 asking questions about physical entailment?
The only way around this (as far as I can see) is to state the following:
Statements (or premises) about the physical may entail further statements (or conclusions) about the physical.
Will even that work for Chalmers?
In order to make that work, the statements which do the entailing would need to be taken as true; and the entailed statements would need to be taken as the necessary consequences of these true statements about the physical. (That said, false statements — or premises — have logical entailments too.) And if the entailing statements (or premises) are taken as true, then they’ll entail other statements — which also have semantic contents which refer to the physical. Thus despite the semantic contents having references to the physical, the logical entailment itself (that is, the relation between entailing statements and entailed statements) can be known to be logically correct a priori (i.e. regardless of truth). However, since the statements are about the physical, the entailment can’t be known to be true — not just valid — a priori if the premises have semantic content about the physical.
Take this example:
This sample before you is water.
That statement isn’t logical. It has semantic content which refers to the physical (or chemical). Yet it can also be said to logically entail the following:
Therefore this sample before you is a collection of H₂0 molecules.
water = H₂0
So all this may mean that Chalmers is implicitly demanding an identity between any physical x and any experience y in order to secure his physical entailment or make it (to use his word) “automatic”. That is, x can only physically 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 physical entailment.
So could there be physical entailment without such an identity? Is it the case that any x can entail any y without x and y being one and the same thing? That is, can we have this? -
If a physical x is the case, then (necessarily) a physical y must also be the case — even when x and y are different things (or events).
Perhaps in the case of the physical and experience, there is no necessity. (As argued by Saul Kripke, etc.) But do we need necessity here? That is, every time there is a given physical x (as in brains, etc. being in a certain states), then there will be experience. Is it necessary that there is experience given this physical x? Well, yes and no. If we have a given physical x, then there is always experience y. 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. In other words, there will no doubt be counterfactual — and even a tiny number of factual! - cases in which such given brain states (the ones which usually bring about experiences) don’t bring about such experiences.
All this leads this question again:
What work are the words “necessary” and “entail” doing in Chalmers’ scheme?