J.R. Illingworth explains in Divine Immanence that consciousness, mind, and the human spirit are realized only materially.
He is not reductive. Thought is not simply the firing of synapses. But “Our every state of consciousness depends, as we have seen, upon the brain, and therefore upon the blood that nourishes the brain, and therefore on the chemical elements that form the blood. Without oxygen, and nitrogen, and phosphorus, and carbon, we could neither think, nor will, nor love” (31).
The human spirit is realized only in “intercourse with spirit,” and this person-to-person communication likewise depends on matter: “Tongue and ear are material things; words are movements of the air; and printing press and telegraph extend their sway. Machinery again, with its coal, and steam, and iron, is ever at work to enlarge the practical dominion of our will; while art art takes up the stubborn elements of earth and transmutes them in its crucible to spiritual things. Hellenic sculptures, Gothic cathedrals, mediaeval painting, modern music, are only modes of matter, when regarded by themselves: yet through them the soul of man has given utterance and permanence to all the varying phases of his inward spiritual story, which else would have been fugitive and dumb” (31).
Writing and speaking, experimentation, action are all necessary for thoughts, ideas, theories to be clarified: “Thoughts float idly across the mind, till they have been precipitated in print; theories remain abstract and uncertain, till they have been tested by experiment; good intentions are of no avail, till they have faced the resistance of the outer world, and in overcoming its opposition become moral acts; and love can never rest, till it has proved its own intensity by a thousand tender, thoughtful, self-sacrificing deeds” (31).
Material expression “strengthens the spiritual fibre, forcing vagueness into outline, confusion into clearness, doubt into decision, hesitation into act.” Matter is “the necessary means by which our spiritual life becomes actual, concrete, real” (31).
A simple point, obvious even. But how much Christian theology has been forgetful of the obvious?