Johansen claims DA 3.2 is consistent with an inner sense theory; Caston, that it presents an account of the structure of an act of sense perception (or 'consciousness'). My plan is to state Johansen's arguments or considerations one-by-one and to place against these arguments or considerations from Caston's paper (or any additionally that I can devise), and then invite readers to contribute their own observations.
Here's a preliminary point, about which interpretation has the more difficult weight of proof.
Johansen takes DA 3.2 to be arguing a relatively weak thesis of 'nothing compels'. That is, Johansen takes the passage to be concerned with whether we need to postulate a faculty, in addition to the five senses, in order to account for our activity of perceiving that we perceive. And he takes Aristotle to conclude that, no, nothing compels us to do so (and then, given that we are not so compelled, parsimony suggests that we not do so). As Johansen stated in his BACAP lecture:
...the project of the De Anima [is] motivated in part by a concern with explanatory economy that is typical of what is commonly known as 'faculty psychology'. Aristotle wants to show how a variety of psychological phenomena can be explained by reference to a few fundamental capacities: no faculties praeter necessitatem.Johansen, then, regards DA 3.2 as arguing for the relatively weak thesis that the phenomenon of 'perceiving that we perceive' carries with it no such necessity.
Caston, in contrast, attributes to DA a positive view that--it is recognized by those who study Caston's paper--is a rich, bold, and interesting thesis (even if Aristotle never held it). As Caston puts it:
Aristotle holds that a single token perception can be about an external object and about itself. This sort of awareness is therefore both intrinsic and relational. (799)For Caston, that Aristotle denies that we need to postulate an 'inner sense' is a consequence of this rich view:
Because a higher-order content is involved, consciousness is still intentional and hence relational. But in so far as only one token is involved, it must be a reflexive relation: in addition to being directed upon an external object, such as an azure sky, the token activity will be directed upon itself. Such awareness is immediate. It is unmediated by any further token activity, let alone a representation of itself; nor is there any transition between the perception and the awareness of it, and hence no inference or causal relation between them. The relation is more intimate: both aspects are essential to any token perception. (778)
For these reasons, Aristotle cannot accept an 'inner sense' or internal scanner whose activities are distinct tokens from the activities they monitor. (779)So the methodological point I wish to make is simply this: since Johansen seeks to get so much less out of the passage, antecedently one should expect that his interpretation would be easier to defend. (Yes, of course, this means nothing if the one interpretation can account for details of the text which the other cannot; but, still, the point is important in judging success and especially in evaluating 'close calls'.)
(Note: Despite the title of his BACAP lecture, it's not correct to say that Johansen regards 3.2 as putting forward an 'inner sense' theory. If I understand him, his view is that 3.2 merely denies that a special sense is required in addition to the five senses, to account for 'perceiving that we perceive'--not that it asserts that what does account for this is an 'inner sense'.)