Humeanism about causation and functionalism about mind

Suppose we combine a Humean account of causation on which causation is a function of the pattern of intrinsically acausal events in reality with a functionalist account of consciousness. (David Lewis, for instance, accepted both.)

Here is an interesting consequence. Whether you are now conscious depends on what will happen in the future. For if the world were to radically change 14 billion years from the Big Bang, i.e., 200 million years from now, in such a way that the regularities that held for the first 14 billion years would not be laws, then the causal connections that require these regularities to be laws would not obtain either, and hence (unless we got lucky and new regularities did the job) our brains would lack the kind of causal interconnections that are required for a functionalist theory of mind.

This dependence of whether we are now conscious on what will happen in the future is intuitively absurd.

But suppose we embrace it. Then if functionalism is the necessary truth about the nature of mind, the fact that we are now conscious necessarily implies that the future will not be such as to disturb the lawlike regularities on which our consciousness is founded. In other words, on the basis of the fact that there are now mental states, one can a priori conclude things about the arrangement of physical objects in the future.

Indeed, this opens up the way for specific reasoning of the following sort. Given what the constitution of humans brains is, and given functionalism, for these brains to exhibit mental states of the sort they do, such-and-such generalizations must be special cases of laws of nature. But for there to be such laws of nature, then the future must be such-and-such. So, we now have a room for substantive a priori predictions of the future.

This all sounds very un-Humean. Indeed, it sounds like a direct contradiction to the Humean idea that reasoning from present to future is merely probabilistic. But while it is very counterintuitive, it is not actually a contradiction to the Humean idea. For on functionalism plus Humeanism about causation, facts about present mental states are not facts about the present—they are facts about the universe as a whole!

(This was sparked by some related ideas by Harrison Jennings.)