A Kantian Aporia?

This just in:

I know you like puzzles in aporetic form, so here you are.

1. My perception involves (though is not necessarily limited to) the immediate awareness of mental phenomena.

2. When I look at the visible surface of this desk, all I am immediately aware of is the visible surface of this desk.

3. The visible surface of this desk is not a mental phenomenon.

All three cannot be true. If (1) is true then my perceiving the desk involves the awareness of mental phenomena. Note that this does not assert that the visible surface of this desk is a mental phenomenon, only that, if it is not, then I must be immediately aware of some mental phenomena in addition to my awareness of the desk.

But (2) says that the visible surface of this desk is all I am immediately aware of. Hence (3) cannot be true.

Likewise, if (2) and (3) are true, (1) is false, and if (1) and (3) are true, (2) is false.

Nicely presented. I agree that the three propositions are collectively inconsistent: they cannot all be true. But there is an interesting problem here only if the propositions are, in addition,  individually plausible.  The more plausible, the tougher the problem. 

(3) is plausible to a high degree. (Plausibility, unlike truth, comes in degrees.)  A desk is a physical thing. The surface of a desk is a physical part of a physical thing. A mind, its states, and its contents are none of them physical.  An occurrent episode of visual perceiving is a mental phenomenon.  So, yes, (3) is highly plausible and I would rank it as the most plausible of the three propositions.  

(2) is the least plausible of the three. It is true that when I look at my desk I do not see my visual perceiving of the desk or of some part thereof.  But it does not follow that I am not aware of my perceiving.  Right now, as I stare at my desk, I am not only visually aware of  (part of) the desk; I am also aware of being visually aware of it.  This is what Franz Brentano calls innere Wahrnehmung, inner perception, which he distinguishes from innere Beobachtung, inner observation. This ongoing inner perception, or rather perceiving, is a simultaneous secondary awareness of the primary 'outward' visual awareness of the (surface of) the desk.

This inner awareness of being outwardly aware of something is not the same as full-blown reflection which one could, but need not, express by saying 'I am now seeing the surface of a desk.'  It also must be distinguished from the type of awareness in which I am outwardly aware of something without being aware of being aware of it at all. Suppose you have been driving for some time, stopping at the red, going at the green, negotiating turns, etc. when you suddenly realize that you have no memory of doing any of those things. And yet your present physical integrity shows that you must have been aware of all those traffic changes. You were outwardly aware via the five outer senses without being explicitly aware of being aware or implicitly aware via Brentano's inner perception. 

And so I solve the above problem by rejecting (2).  (2) is the least plausible of the three and a very strong case can be made for its being false.

(1) leaves something to be desired as well. Later on this.

So we don't have an aporia in the strict sense, an intellectual impasse, or insoluble problem.  And even if we did, it is not clear what this has to do with Kant.