I. Response to the Question

7. In this question it is plain that the Father and Son are one principle of the Holy Spirit. This was made clear in the General Council of Lyons under Gregory X, as is plain in the Extra, ‘On the Supreme Trinity and the Catholic faith’, and it is today in book 6 of the Decretals [Sixth Book of the Decretals of Boniface VIII lib.1 tit.1 ch. un].

The reason for this truth is as follows, that, as was said in distinction 11, the Father has first in origin the act of fecundity of the intellect before that of the will [I d.11 n.13]; in that prior stage there is communicated to the Son the same fecundity as is in the Father, because in that moment of origin - in which the Son is produced by the fecundity of the intellect - there is communicated to him by the Father whatever is not repugnant to him, and so the fecundity of the will is communicated [ibid. n.12]; therefore, in the other moment of origin, when a person is produced by the act of the second fecundity (namely of the will), that person is produced by the Father and the Son as altogether by one principle, because of the one fecundity of the productive principle in them [ibid. n.18].