Love triangles usually mean that no one wins.
In the end, no one ends up married. Not the imposter, not the wife, not the husband. All three are victims of the wife's indiscretion, but actually, since her indiscretion was the result of her mistreatment, the impetus falls on the husband. He was so poor of a husband to his wife that she was willing to suspend her disbelief to be treated a little better.
Marriage is what you make it.
Again, the central dilemma of the novel is itself evidence for the fact that marriage is not necessarily a perfect thing. By mistreating his wife and by staying away from home for so long, Martin Guerre loses his wife to her own desires for a better life, and the imposter who came in his stead.
Deception starts within the self.
Another interesting aspect of the novel is that the main character, the wife, that is, has a good reason for pretending the imposter is actually her husband. This causes her to actually suspend her disbelief, making a subconscious choice to let the farce go on, because the imposter was accidentally meeting her emotional needs. If her needs had been met by her husband or by herself, she would not have been prone to this kind of deception.
Circumstantial evidence is pretty much worthless.
If the wife of Martin Guerre couldn't even remember the face of her husband, how can men use circumstantial evidence in a court of law? The problem is subjectivity. Whenever we believe we will benefit by indulging a lie, we often do it, fooling ourselves along the way.
