Gabriel is the spirit-being whose work is incarnation. His activity turns spirit into matter. Gabriel directs mankind's attention to the physical world and sense perception.

"It is no accident," the Meggid explains, "that Gabriel has always been recognized by Christians as the angel of the Annunciation; for incarnation, the becoming flesh of spirit, is the core of his impulse and activity. For the ordinary run of mankind he is effective in all that they develop through the operation of physical heredity" (UV 40).1

The Meggid has more to say concerning the influence of Gabriel:

Dwell on the full meaning of the word incarnation. It does not refer only to human flesh, or even only to flesh. It refers to the whole world of nature, in so far as that is perceived through the senses; and it was to this world of the senses that Gabriel directed the earnest gaze of mankind. It is this world that they have been minding more and more through the last three or four hundred years--so assiduously, at last, that they have begun to believe there is no other. And even that there has never been any other.
"Had they not done so," the Meggid adds, "they could never have built up their technological civilization, with its evil and its good" (UV 40-41).
See in particular Unancestral Voice, passim.
1Barfield goes on to say "During the three or four centuries of Gabriel's hegemony the forces of heredity worked very strongly through the whole of Western civilization. . . . Men experienced his working as the warmth with which they felt all that linked them together in this way-with their ancestors, with their children and their children's children, and with each other, in so far as the others were of the same blood" (UV 40).