Enneads III.6: Of the Impassibility of Incorporeal Entities (Soul and and Matter)
The Sterility of Nature Indicated by Castration
That name indicates the difference between matter and a mother. To those who, refusing to be satisfied with superficialities, insist on thoroughness, they thus signified in as precise a manner as possible (without lifting the veil of) obscurity, that matter was sterile, although feminine also to the extent at least that matter receives, without contributing to, the act of generation. They indicated it by this, that the (Galli) who surround Cybele are not women, but neither are they men, possessing no power of generation; for by castration they have lost a faculty that is characteristic only of a man whose virility is intact.