“And here we must consider, that the divine Nature did not assume an humane Person, but the divine Person did assume an humane Nature: and that of the three divine Persons, it was neither the first nor the third that did assume this Nature; but it was the middle Person, who was to be the middle one, that must undertake this mediation betwixt God and us. which was otherwise also most requisite, as well for the better preservation of the integrity of the blessed Trinity in the Godhead, as for the higher advancement of Mankinde by meanes of that relation which the second Person the Mediator did beare unto his Father. For if the fulnesse of the Godhead should have thus dwelt in any humane Person, there should then a fourth Person necessarily have been added unto the Godhead: and if any of the three Persons, beside the second, had been borne of a woman; there should have been two Sons in the Trinity. Whereas now the Son of God and the Son of the blessed Virgin, being but one Person, is consequently but one Sonne; and so no alteration at all made in the relations of the Persons of the Trinity.”
James Ussher, Immanuel.