Disclaimer: I don't own The Princess Bride, but I do own my True Love for Westley!
Early on in their marriage, Westley found several flaws in Buttercup. Actually, he found more than several flaws, but for the sake of his undying devotion to her he decided to pretend that the other ten or fifteen flaws didn't exist.
Westley was a firm believer in True Love. He had survived pirates, the Cliffs of Insanity, a mad Sicilian, The Machine, and even a brief and undocumented encounter with ninjas all for the sake of Buttercup, and he honestly considered the trials he endured worth it. Well, maybe not the ninjas…but that's beside the point.
The point is, despite being romantic Westley was a realist at heart – one of the last. He realized very quickly that relationships, even relationships based on True Love, could have no hope for survival if subjected to constant nitpicking and fingerpointing. So, after ruminating over this realization for several weeks, Westley resolved to overlook most of his darling's faults for the sake of his undying devotion to her. This worked for many, many years and innumerable, incalculable days, until he didn't even notice her minor flaws.
He just saw her Top Two.
Soon, those Top Two became Westley's Achilles's heel, his Trojan Horse, his Delilah. He didn't actually know who any of those people were, but the general feeling was the same – shock followed soon after by misery. What was he to do when faced with his wife's two major flaws? After some more incalculable days, Westley decided to go with a tried and true remedy: ruminating.
Problem number one? Buttercup's brain – or rather, her lack. While Westley loved his sweet lady to the Fire Swamp and back, even he could admit that she wasn't quite the brightest torch in the bracket. Or the sharpest knife in the kitchen. Or any of the other usual expressions employed to describe brilliance in the human mind.
It wasn't like he expected her to take up charting galaxial constellations, or quoting quantum physics equations while balancing a book on her head – books and Buttercup were a dangerous combination – he just wished he could sometimes see a spark of something in her eyes. Even if it was only once in a while, he wanted some sort of reassurance that there was still a light turned on upstairs.
Was that so much to ask?
Problem number two: Buttercup's naiveté and the trouble it caused. Because yes, only his Buttercup would consider stopping to converse with three strange men in the middle of a deserted forest a safe pastime; only his Buttercup would think that giving herself up to a false marriage would save him from her pig fiancé; and only his Buttercup would trust selfsame pig to keep his word about delivering certain letters to a certain ship.
His True Love could certainly be an dunce at times.
Of course, he came for her as he always did and everything worked out swimmingly, but still – it was the sheer principle of the matter! She really had no survival skills whatsoever. Perhaps it was the result of some deadly flaw in her genetics, and she hadn't been meant to live past age fourteen. Perhaps she was a weakest link in nature and his interference had saved her from death. Well, he had saved her from death, but that's beside the point.
The point being, no one could argue that Buttercup had beauty in place of brains. (Buttercup herself had tried to disprove this once, but since the use of debating skills requires a brain she didn't get very far).
And yet, despite it all, Westley had come to a fairly positive conclusion: he still loved Buttercup. Whether because of fate, or destiny, but certainly not because of her cooking, he was linked to her for eternity. In fact, he was pleased that she couldn't quote quantum physics, because their love defied those tightly-laced laws and no amount book sense could explain it. He was pleased with her naiveté, because it kept their love fresh and pure, in a way that hardened cynicism never would.
Most of all, after many, many years and innumerable days of ruminating on the subject, Westley was pleased to realize that Buttercup's two biggest flaws were the Top Two reasons that he had stayed unequivocally and irrevocably in True Love with her.