Progenitive

(adj) Having the ability to produce offspring.

//Say it to Father will you I will am my fathers Progenitive I invented him created I him Say it to him it will not be for he will say I was not and then you and I since philoprogenitive// TSAF (122)

Quentin's imagined conversation with Caddy challenges their paternity. Quentin imagines, "I am my fathers [son]" will be refuted with "he will say I was not." Quentin fantasizes that he is not Jason's son because then he and Caddy would not be siblings and his incestual obsession with her would be acceptable.