Soldier, priest, and diplomat; gallant, greedy, and cunning; Aramis took the good things in this life as steppingstones to rise to bad ones. Generous in mind, if not noble in heart, he never did ill but for the sake of shining a little more brilliantly. (34.6)
Dumas is paying Aramis a back-handed compliment in the above quote, and the same ambiguity about Aramis's character definitely comes out in the sections below.
Consider each of Aramis's actions with regard to his friend:
We're beginning to believe that all that mushy stuff Aramis said to Philippe about loving him, respecting him, and wanting to serve him may not have been the truth. Did Aramis really think thigh highly of Philippe, or did the former Musketeer want to control the monarchy and the "souls" of the people, as he once claimed. Once his perfidy is discovered, Aramis bails on Philippe like a rat bails on a sinking ship, without a backward glance. Does the fact that Aramis bailed on Philippe mean that he never supported the false King in the first place? You decide.
Unlike D'Artagnan, it's pretty clear that Aramis would pick career advancement over his friends any day. Just look at how he treated Porthos and Philippe. His desire to have influence over the people's "souls" may have gotten in the way of his friendships. Think about the fact that Aramis is the only one left alive at the end of The Man in the Iron Mask. What kind of paradigm is the novel espousing when being unscrupulous means you get to live and being brave and loyal means you get to die? Just a thought for you to consider.