62 qui Patre et filio auctoribus confitendus est; A comparison with dum et usum et auctorem eius ingnorant in § 4 makes this appear the probable translation. It might, of course, mean confess Him on the evidence of Father and Son.
12 This is an argument against the objection that God, if Christ is His Son, must have suffered loss. If God is His Father and the sole source of His existence, Christ must have come into being by separation from the Father; i.e. the Father must have suffered diminution and lost His completeness. The answer is that a woman-and a fortiori the Virgin, who was the only human parent Christ-suffers no loss of bolily completeness through becoming a mother. There is no allusion to the belief in the perpetual virginity of the Mother of our Lord.
20 Substitutio; this word seems, except in technical senses of the law, to be very late and very rare. The only meaning, and that one ont attested in the dictionaries, which will suit this passage, seems to be that of the jackdaw dressed in peacock's feathers.