245. The nature of the influx of light into the three degrees of life in man which belong to his mind, shall now be shown. The forms which are receptacles of heat and light, that is, of love and wisdom in man, and which (as was said) are in threefold order or of three degrees, are transparent from birth, transmitting spiritual light as crystal glass transmits natural light; consequently in respect to wisdom man can be raised even into the third degree. Nevertheless these forms are not opened except when spiritual heat conjoins itself to spiritual light, that is, love to wisdom; by such conjunction these transparent forms are opened according to degrees. It is the same with light and heat from the sun of the world in their action on plants on the earth. The light of winter, which is as bright as that of summer, opens nothing in seed or in tree, but when vernal heat conjoins itself to that light then the heat opens them. There is this similarity because spiritual light corresponds to natural light, and spiritual heat to natural heat.