C. S. Lewis discussed in depth God’s becoming man in Miracles. I am sharing a series of comments from his book that speak to this reality. I refer the reader to his chapter entitled, “The Grand Miracle”:
What can be meant by “God becoming man?” In what sense is it conceivable that eternal self-existent Spirit, basic Fact-hood, should be so combined with a natural human organism as to make one person? And this would be a fatal stumbling-block if we had not already discovered that in every human being a more than natural activity (the act of reasoning) and therefore presumably a more than natural agent is thus united with a part of Nature: so united that the composite creature calls itself “I” and “Me.” . . . In other men a supernatural creature thus becomes, in union with the natural creature, one human being. In Jesus, it is held, the Supernatural Creator Himself did so. . . . We cannot conceive how the Divine Spirit dwelled within the created and human spirit of Jesus: but neither can we conceive how His human spirit, or that of any man, dwells within his natural organism. What we can understand, if the Christian doctrine is true, is that our own composite existence is not the sheer anomaly it might seem to be, but a faint image of the Divine Incarnation itself - the same theme in a very minor key. . . . We catch sight of a new key principle - the power of the Higher, just in so far as it is truly Higher, to come down, the power of the greater to include the less.
I address extensively in my books, especially in The Boundless Love of God: A Holy Spirit Story, the “how” of this “composite existence,” drawing upon current findings of neuroscience and information theory to obtain at least a partial understanding. Most of all we now have the ability to understand that the “coming down” of the Holy Spirit to indwell the human spirit to give Counsel to the human soul is a reality in which we can have evidential faith in our time.