In a response to my previous post, on Acausality and the Scientific Mind, a commenter said: “The computationalist position necessarily entails that subjectivity does not really exist, and what looks like subjectivity is a mere illusion without causal force.”
There are, I’m sure, many vulgar and stupid versions of computationalism that have this as a dogma. But it is not at all difficult to construct a computationalist model in which there are features that map to “subjectivity” and have causal force. Here is a sketch:
Human beings have minds that are persistent information patterns of very high complexity. These patterns evolve over time, incorporating memory (both memories about sense data and memories about features of past mental states). The path can in principle be modeled as a computation in which the inputs are the present mental state and sensory inputs, and the result is a succeeding mental state. (The last sentence is the computationalist position.)
The computational path of a mind in the space of its possible mental states is chaotic, in the sense that its future has sensitive dependence on unmeasurable features of its present state (it is not significant to my argument whether the indeterminacy is quantum, classical, or due to computational intractability). The mind is therefore, as a whole, intractable to prediction.
Now we face the procedural question of how we identify a mental state. We do this in the same way we identify the state of a collection of matter: by measuring observable consequences. We observe that mental states of different people can be grouped into equivalence classes by observable consequences. (If this were not so, language, art, and communication in general would be impossible.)
Next, we observe that important features of our mental states are not intractable to prediction. We know this because people can form predictive models of each others’ mental states; in fact people rely so heavily on this ability that there is a strong case we evolved into sophonts in order to get better at it.
It is important, and bears emphasizing at this point, that we now have a model of mind in which (a) some features of its state at any given moment are tractable to prediction, (b) other features are not tractable to prediction, and (c) the tractable and intractable features are causally entangled with each other and are both inputs to ongoing computation.
Now I propose a definition: the “subjectivity” of a human being is that portion of his or her evolving mental state which is intractable to prediction by any observer.
I think it is not difficult to see that this definition accords with our intuitive notion of “subjectivity”. But here is the important point: As so defined, subjectivity is not a mere epiphenomenon or illusion. It has causal force because it is an input to the computation of future mental states which have observable consequences.
See, that was easy. Subjectivity reconciled to computationalism in less than 20 minutes of writing. A lot of philosophers of mind seem to be remarkably thick-headed.