Isaac

Isaac wrote On the Holy Trinity and a book On the Incarnation of the Lord, in a very obscure style of argument and involved language. He maintained that three persons exist in one Deity in such a way that each has something proper to itself that another does not have. The Father has this property, that he himself, being without source, is the source of the others. The Son has this property, that, though begotten, he is not later than the one who begot him. The Holy Spirit has this property, that he is neither made nor begotten, but is nevertheless from another. Of the incarnation of the Lord he writes that the person of the Son of God is believed to be one, while yet there are two natures existing in him. [a]