Today I will again respond to defenses of externalism, both from here, and some that I have made up on my own.
The first objection takes the following form: although you may have shown that we are not conscious of the effects of externalism on the mind perhaps there is some unconscious, non-causal, connection between our minds and the external world. There are two ways to respond to this, a weak way and a strong way. The weak way is to define thoughts as necessarily being part of consciousness. Although we may have unconscious motivations, dispositions, ect, none of these things are thoughts. Thus by definition if externalism has any relevance to the contents of thoughts it must be part of our consciousness, and thus noticeable by us. I call this the weak response because while I think it is obvious that it is essential to a thought that it be conscious I admit that not all philosophers see it this way. The strong response is to run another experiment designed to reveal if there are any unconscious impulses that are attuned to the existence of the bubble. We do this by asking the subject to guess whether the bubble has popped or not. If they guess correctly we give them a piece of chocolate, and if they guess wrong we smack them with something blunt (make sure your volunteers are willing). If the person never achieves better than 50% accuracy this is pretty good evidence they aren’t sensitive, even unconsciously, to the existence of the bubble. (Such experiments have a well-known history of revealing unconscious knowledge/sensitivity.) Although you can run this experiment for yourself (and I have), you can also take a look at professional studies of “esp”, some of which are set up in a similar manner. Performing this experiment, or looking up the results of previous research (but remember to find studies from neutral parties, don’t expect the esp foundation to conduct unbiased studies) reveals that if there is an unconscious awareness of the bubble it is small enough to be hidden by experimental error.
The next objection is as follows: “Take the classic example from Putnam. … Say someone can’t tell the difference between an elm tree and a beech tree. They want to buy an elm tree. Someone sells them the tree but later someone tells them that it was actually a beech tree. Now their phenomenal experience might be identical. (The tree looks the same to them) But clearly the intent wasn’t the same. They didn’t want an elm tree. They wanted a beech tree. Thus a difference is made, but it is a difference that is made in the future.” This is supposed to show that internalist accounts are missing something, namely the difference between the person who wanted the beech tree and the person who wanted the elm tree. If internalism really couldn’t give an account of this I would agree that it should be discarded. However simply reading the example closely reveals that there is indeed phenomenal different even when the person cannot physically distinguish between them: they have expectations as to what it will be called by other people (one will be called “elm” and one will be called “beech”), specifically then the person sees the tree and thinks “this is a tree that is called an elm”, even if they don’t know which physical characteristics distinguish one kind of tree from another (because they were told it was an elm by the sales person). Remember that our experience of something is not just how it looks or how it feels, our phenomenal conception is all of the properties that we associate with it, and that includes what it is called by people.
A third possible response is that the effect of intentionality, whether conscious or unconscious, is simply too small to be noticed (a possibility I briefly mentioned above). This is a strange position to hold. We could of course run more experiments to reduce the experimental error, but of course this doesn’t eliminate the possibility of such an outside influence, it just makes it vanishingly small. The best response to give to such doubts is perhaps an appeal to Occam’s razor, specifically that it is simpler to assume that internalism is a complete account of how the mind works than to assume that internalism explains most of how the mind works with just a touch of externalism thrown into the mix.
Another possible response is to defend intentionality as not determining the content of specific thoughts but the content of “classes” of thoughts. Under this interpretation it is not a specific thought about the bubble that has its content determined by the intentional relation but the content of a class of thoughts that is the “template” from which all my specific thoughts about the bubble are derived. This interpretation would still fall into the same problems facing the standard theory, so we make the additional assumption that this class is “timeless”, specifically that it is related to the bubble when the bubble existed, but because the class itself is timeless it can provide us with the content for our thoughts even when the bubble is gone. Of course this is basically the same as reintroducing the theory of forms in another guise, and thus I would reject it for the same reasons that we doubt the existence of the forms. (For example because the timeless cannot affect that which changes over time.)
Let me end with a challenge to externalists. If the external world does have a real, non-causal, effect on our minds design and run an experiment that shows the existence of that effect, the results of which would surely throw doubt on the internalist position (and would shut me up, as well as revolutionize physics).