Dr. E. L. Mascall on the reality of the Incarnation

Since human nature, in any individual, is not given from its beginning in a fully developed state but develops from the unrealized potentialities of the original fertilized ovum through birth, infancy, childhood, and adolescence to its climax in adult manhood, we must surely hold that the mentality of Jesus, like that of any other human being, developed pari passu with the development of the bodily organism. To say this is not to imply that it was defective in the early stages; on the contrary, at each stage it was precisely what at that stage it is proper for human nature to be. It is surely a valid insight that asserts that you must not try to put an old head on young shoulders. It is not simply a discovery of modem anthropology that mental and physical (especially cerebral) functioning are intimately and intricately allied; it is inherent in the traditional Christian belief that a human being is not a pure spirit temporarily encapsulated in a body but is a bipartite psychological unity... A modem discussion of Jesus's human knowledge will need to take account of all that is now known about the psychophysical structure of the cognitive process and about the development of human mentality from its beginning in the fertilized ovum to its culmination in adulthood.

While Jesus’ human nature is more and not less genuinely human for its assumption by the Person of the eternal Son of God [as set forth by the Council of Chalcedon], it may for that very reason be expected to manifest powers and capacities which outstrip those of human nature as we normally experience it in ourselves and in others. Some of these powers and capacities may pertain to Jesus simply because his human nature is unfallen and perfect, whereas ours is fallen and maimed, and, though redeemed, is still in process of recreation and restoration. Others may pertain to it because its Person is the divine Word, because “in him the whole fullness of deity dwells bodily” (Col.1:19). It may be difficult to discriminate in any given case between these alternatives; nor, I think, will it greatly matter, provided we keep a firm grasp upon the principle that, even in the supreme example of the Incarnation, grace does not suppress nature but perfects it. (Whatever Happened to the Human Mind? (London: SPCK, 1980), p. 45.)