Who is Rupert Birkin from Women in Love and what is their importance?

Rupert Birkin is the intellectual heart of the novel. He is a school inspector, with very particular ideas about man in industrial society, and the death process he is engaged in. Birkin wants an ultimate marriage with a woman. It turns out to be Ursula and he wants to be beyond himself, beyond just caring for the other's comfort. He wants to be accepted in his contradictions, and he wants to accept a woman in hers - beyond the mere personalities of himself and the other.