Matter does not mean "closed to the spirit" or "a place where God is not found." If we picture the universe as "the opposite of God," then we land in the Cartesian dilemma between spirit and matter. Start with the wrong picture and definitions, and suddenly we cannot see how God, angels, saints, or our own soul can "enter" the world. Donceel: "We must get to God immediately. We cannot start with a universe that is alienated from God; we will never get Him 'into' such a world."
Matter means "totally open to the spirit."
Matter cannot oppose God's will, nor lock Him out of the universe.
Matter is filled with meaning. Matter is a manifestation of God. It is caused by God. He dwells in everything He has created. Matter is the sacrament of spirit.
Matter blocks light, but radiates glory.
We never see pure matter; all we can observe are forms of matter. "Matter" is a metaphysical concept that has no meaning apart from the concept of "form."
Matter is not the opponent of spirit; it is a realm that spirit rules.
GKC on Victor Hugo: "For to him there is neither a large thing nor a small one; he has abolished the meanest and most absurd of all human words, the word 'insignificant': he knows that it is impossible for anything to signify nothing."
It is not matter that opposes God, but materialism, a false philosophy of the material universe.
Descartes' fatal error was to suppose that matter can be understood apart from spirit. Thinking spatially--which is natural for a geometer!--he defined matter as that which has extension and spirit as that which has no extension. There was then no way for him to "picture" how the soul could "come into" the body.
We have to think causally instead of spatially, and train ourselves to let go of misleading images.