An Algebraical Conundrum

Alcibiades: I approve of A.
Socrates: But then surely you have a reason for your approval?
Alc.: Certes.  I approve of A because it lacks property X!
Soc.: But then you must also approve of B, because B also lacks property X.
Alc.: What?  No!  That is awful.  A is worthy because of... because of condition Y.
Soc.: Is it Y now?  But condition Y applies also to action C.  So you must approve of...
Alc.: I do not!  How dare you compare A to C!
Soc.: It was thou who made the comparison, bold Alcibiades, when you said that it was condition Y that made A worthy.  Since C also follows from condition Y, then C must also be worthy.  If it is not so, then there must be some other reason why A is acceptable to you and B and C are not.
Alc.: Surely.  A is acceptable because of reason Z.
Soc.: You are fast running out of reasons.  And do not call me 'Shirley.'  But you do wit, do you not, that if Reason Z is true, the D must also follow.
Alc.: D is an abomination.  You cannot be saying that A is the same as D!  That is a vile insinuation.
Soc.: Too bad they stopped teaching analogies a generation ago.  To say that if A is justified by D, then D is just as well justified is not to say that A and D are the same thing; only that the reasons you present to justify the one are also sufficient to justify the other.  You cannot cite X to support A and then ignore it in the case of B.  You must think things through -- break on through to the other side, as the Poet once said.  Or else do not lean upon that particular reed.
Alc.: Very well, then.  I deny all reasons, lest they be argued against my other commitments.  I assert the acceptability of A, simply as a brute fact.  I approve of it simply because I approve of it.
Soc.: But then you are being unreasonable - literally.  You desire A because you desire it, and nothing must stand between A and your unrestrained appetites.  Begone, thou Nietzschean lout! 

Plato: Solve for A.