But probably the cause of John's transgression is much deeper than base physical reasons.
It's also quite possible that John Proctor was attracted to Abigail's subversive personality. Miller seems to hint at this in the first scene where we see them together. Abigail tells John that all about witches isn't true. She and the other girls were just in the woods having a dance party with Tituba. Miller writes:
Enter: Abigail, the play's antagonist. traipsed in to John's life (while Mrs. Proctor was super ill, btw) and, before he knew it, his good life was bad, bad, bad. John made the mistake of committing adultery with her. To make things worse, it was also lechery (Proctor was in his thirties and Abigail was just seventeen—yuck). All it took was one shameful encounter to destroy John's most prized possession: his self-respect.
When we first meet John Proctor halfway through Act I, we discover a man who has become the thing he hates most in the world: a hypocrite. He is caged by guilt. The emotional weight of the play rests on Proctor's quest to regain his lost self-image, his lost goodness. In fact, it is his journey from guilt to redemption that forms the central spine of The Crucible. John Proctor is a classic Arthur Miller hero: a dude who struggles with the incompatibility of his actions with his self-image. (Willy Loman of , Eddie Carbone of , and Joe Keller of all have similar issues.)
John Proctor, The Crucible's protagonist, has some major issues. But we can see why. Back in the day, he had everything your average Puritan man could want: a farm to ceaselessly toil upon, three sons to discipline, and a wife to make a home with. Proctor was who spoke his mind. Around town, his name was synonymous with honor and integrity. He took pleasure in exposing hypocrisy and was respected for it. Most importantly, John Proctor respected himself.