At least, I think he's meant to be Mr. Perfect -- as long as you don't dwell too long on his vaguely prissy, controlling personality (he initially refused to go out with Carrie because she was a smoker). But then Big came back into the picture, tail between his legs and miserable in his marriage; obviously in need of a man who not only allowed her to smoke, but lit her up, too, Carrie had a secret affair with Big, wrecking Big's marriage and costing her Aidan.
This season, lonely Carrie wooed Aidan back and undercurrents of emotional sadomasochism began bubbling up in their relationship. Aidan played passive-aggressive head games with Carrie for breaking his heart; wracked with guilt, Carrie overcompensated, trying to be the most contrite, patient, no-strings girlfriend in the world. Despite her guilt, though, and her salvaged relationship with Aidan, Carrie still can't manage to kick Big out of her life. She remains friends with him, or so she thinks -- this man has no use for female friends; he's courting her again, and she cant see it. (In one episode this season, she even forced Aidan and Big to try to be friends; Noth and Corbett's scenes of antler-knocking stud rivalry were played with exquisite comic discomfort.)
In the summer finale, when Carrie told Big she was marrying Aidan, he chortled and advised her that Aidan is the wrong guy, and furthermore, "It'll never happen ... you're not the marrying kind." What he meant was, she's not the marrying kind, if marrying means hooking up with a saintly, self-righteous bore like Aidan.
Carrie and Big (or, maybe, Parker and Noth) spark, parry and smolder together like a couple from a screwball comedy of the '30s; I'd love to see the Big-Carrie-Aidan triangle turn into a modern "Philadelphia Story." Carrie and Big, both pleasure hounds, both imperfect, are completely honest and relaxed with each other. But Carrie is neither honest nor quite herself with Aidan. She finds it strangely easy to lie to him, even though she knows the trouble dishonesty has got her into before. He asks her who was on the phone, and instead of telling him it was Big, she says it was Miranda. He asks her if she ever had an abortion and she immediately says no. (She does end up telling him the truth, finally.) Is this the guilt over cheating on him coming back to roost? She's terrified of appearing less than perfect in his eyes; she is consumed by the feeling that Aidan is "good" and she is "bad."
Doesn't Aidan strike you as a sly mofo, subtly suffocating Carrie in the ties that bind, in her own guilt, by being so accommodating, so good, so forgiving? Before the marriage proposal, Aidan made her an economic proposal -- he would buy her apartment, which was going co-op and which she couldn't afford, and they would live together. Carrie agreed -- so now, like many "unliberated" women before her, Carrie will be dependent on her man for the very roof over her head. Aidan may look like Prince Charming, but he's not. He's bad for her and I think Carrie knows it. But she's determined to prove to Big that she is so "the marrying kind," even if it's a doomed marriage to the wrong guy. The clothes may still dazzle and the dialogue may still snap, but, lately, "Sex and the City" is confidently thrusting its self-styled feminist heroines into "put up or shut up" emotional and romantic quandaries. And, sometimes, the truth isn't pretty.