Man like, he did not understand to the full that great and wonderful enigma, which has puzzled the world since primeval times: a woman's heart.
The eternal contradictions which go to make up the complex nature of an emotional woman were quite incomprehensible to him.

Juliette had betrayed him to serve her own sense of what was just and right, her revenge and her oath.

Therefore she did not love him.
It was logic, sound common-sense, and, aided by his own diffidence where women were concerned, it seemed to him irrefutable.
To a man like Paul Deroulede, a man of thought, of purpose, and of action, the idea of being false to the thing loved, of hate and love being interchangeable, was absolutely foreign and unbelievable.

He had never hated the thing he loved or loved the thing he hated.

A man's feelings in these respects are so much less complex, so much less contradictory.
Would a man betray his friend?
No--never.