The title character doesn't seem to be much more than a plot device to hammer the final nail in Fouquet's coffin and to explain Aramis's fall from royal favor. He is an honorable man who had the extremely bad luck of being born two seconds after his twin brother, but we can't say much more than that. The truth is that we don't see Philippe for much of the novel. He is imprisoned for the vast majority of the action, and really only surfaces as the counterfeit king for a few chapters. We just don't have enough time to get to know him as a character.