What does the arnolfini wedding portrait have to do with humanism?

Humanism in renaissance times is when the artist painted human acheivments or human potential into their artwork. The Arnolfini Wedding represents this because Jan Van Eyck painted himself into his own painting, in the reflection in the mirror. Also, how he signed his name so big and visibly on the wall, which also might hint that it was the legal document of the marriage. But that topic still has much debate.