There are various reasons why it might be appealing to assimilate control consciousness to a form of sensory consciousness. Of our various mental states, the ones most vividly present to us are our states of sensory consciousness. Sensory consciousness, especially visual consciousness, is, from the point of view of science, perhaps our best-understood form of consciousness. Further, the institution of science itself is influenced by a long tradition of empiricism, an early motto of which is that there is nothing in the mind that is not first in the senses.
What, then, would it mean to assimilate control consciousness to sensory consciousness? It is natural among researchers to take deliberate bodily motion as a basic and paradigmatic case of an action. And the most natural way to assimilate consciously moving parts of one’s own body to a form of sensory consciousness is to do so in terms of sensory feedback from the muscles, tendons, and skin as the body parts in question are moved. Now, part of what makes the pure perceptual model pure is its denial of any direct contribution of a motor command signal to the subjective aspect of control consciousness. And it is precisely this denial that leads to the key weakness of the pure perceptual model of control consciousness.
We can perhaps best appreciate the shortcomings of the pure perceptual model by noting that the pure perceptual model entails the following two possibilities.
Possibility 1: Two subjectively indistinguishable arm movements that, though subjectively indistinguishable, differ objectively in that one was the consequence of the subject’s motor command and the other was unaccompanied by any motor command of the subject.
Possibility 2: An arm movement resulting from the subject’s issuing a motor command but, due to effects of anesthesia, is unaccompanied by sensory feedback, and, lacking sensory feedback, the subject is completely unaware of having either moved or even having tried to move his or her own arm.
In some sense of possibility, say, logical possibility, (1) and (2) represent genuine possibilities. However, in a sense of possibility more relevant to scientific interests, say natural or empirical possibility, there’s good reason to believe that neither (1) nor (2) are possible. For example, contra (2), as pointed out by Prinz (2007, p. 344) and Peacocke (2007, p. 359), a subject may be quite aware that they are moving a body part even though they are not perceiving the part due to either local anesthetic or severing of afferent nerves.
It is tempting to conclude from such cases that motor commands are not irrelevant to control consciousness in the way entailed by the pure perceptual model. However, to put the point in a way that is more neutral between the motor theory and the imagery theory, sensory input alone seems insufficient for control consciousness. Something more than sensory input is needed to account for such cases. The motor theory holds that the something more is the contribution of motor commands. The imagery theory holds that the something more is the contribution of sensory imagery. In the next post, I examine these two proposals in further detail.
1. Control Consciousness