The 'Two Minds' Problem
William James had a difficulty that he never managed to satisfactorily resolve: how can two minds simultaneously experience the same object, without overlapping? Heft (pp164) describes the problem thus:
Perceiving is a direct relation between a knower and an object (the fundamental principle of radical empiricism)James wanted to maintain all three of these, but couldn't see how to have them all be true; if two people perceive (i.e. are in direct relation to) an object, then that object now constitutes part of two fields of experience; in other words, minds overlap. For James, this then gave each mind access to a lot of the other, via the various relations connected to the part that overlapped. His initial attempt at a solution (in the essay 'How Two Minds Can Know One Thing' is that while the percept is, indeed, directly perceived and a potentially problematic part of everyone's experience, conscious experience itself is conceptual, i.e. an abstraction from a percept. Specifically, to become part of conscious experience, the object must be selected from the stream of experience and because this is something each individual must do, the actual object of consciousness is adequately insulated.
The thoughts of individuals are insulated from one another (a primary attribute of consciousness that sustains individual choice and action)
Two (or more) individuals can experience the same object at the same time (the phenomenon to be explained)
The ontological problem that now emerges is this: you now have each person with their own experience of the object, which requires one version of the object for every observer if you wish to avoid the dualism of representation. This means objects are multiply realised, one per observer, and ontologically, this entails pluralistic panpsychism, a flavour of idealism (i.e that which is real is mental). James was intending for radical empiricism to be a neutral monism, in which there is one type of stuff that is neither mental nor physical (and thus avoiding the dualism that postulates these are the types of things you are allowed to claim as real).
So James' programme of radical empiricism stumbled, and James never solved this. Heft proposes that Gibson has a solution, in the form of the ecological optics that serves as the proposed mechanism for implementing James' claim that relations are real, perceivable and thus intrinsic to experience. The solution is simple: objects are indeed multiply realised, but in the optics, not the world.
Objects are (optically) specified by invariants in the optic array, which are revealed as invariant over transformations incurred by motion (of the organism or of the object). This invariant information which specifies an object is available from multiple places within the array; there are many points (or paths) of observation over which the invariant can be revealed, and therefore the object can be specified in multiple locations in space. Two observers are said to be perceiving the same object when they have successfully sampled the required information, which they can do at the same time but not necessarily from the same place. Each observer is therefore directly perceiving the object from two of the locations from where this is possible, and the specific relation Observer 1 is in with the object is related but not identical to that for Observer 2.
This seems straight-forward: Gibson's mechanism (ecological optics) provides a straight-forward and fairly common-sense solution to a critical problem for radical empiricism. Two things occur to me with regards to this:
1. Multiple realisation seems to be an uncomplicated feature of dispositions, which, if I've read this right, is very helpful - it bolsters Gibson's approach as well as the dispositional ontology for affordances. This will hopefully become more clear to me as I try and read the philosophy literature on dispositions in more detail.
2. While I'm happy with this solution, it occurs to me, at least in passing, that the 'problem' of two minds may actually be no problem at all; quite the contrary. William James seemed to think that if minds overlapped, they would each have access to large parts of each other . Heft, when describing this problem, is also pretty straight-forward about this:
But this possibility simply does not square with the facts of daily life. If an individual's experience is not insulated and personal, but can overlap with that of another when they are both perceiving a common object, then at such times each individual would also have access to additional contents of the other's conscious experience (through the lines of relation that connect an individuals percepts and concepts). As a result, the claim...must be rejected. (Heft, pp165)This sounds a lot like a fact of daily life to me, actually. When I look at an object that another is looking at, I do, in some sense, know quite a bit about what the other person is thinking (varying with how well I know the person, what the object is and so on); this sounds like empathy, or mind-reading (the kind cognitive psychology thinks we're up to all the time). For a representationalist psychology, we truly are insulated from one another; we only experience the world indirectly, via personal representations, and thus common experience is a problem to be solved. This is a very hard problem and is thus a hot topic; but the solutions tend to be theory of mind or mirror neurons, or mirror neurons as the neurophysiological basis for theory of mind. I don't have time to rant about these here, but at a first (very light) pass, the so-called 'problem' of two minds actually resembles a direct perception solution to the problem of common experience. Feel free to weigh in on this; I'm not especially committed to it but it strikes me as potentially quite interesting.