Note how this view avoids both pitfalls; the alternative abysses of impotence. The mind is not merely receptive, in the sense that it absorbs sensations like so much blotting-paper; on that sort of softness has been based all that cowardly materialism, which conceives man as wholly servile to his environment. On the other hand, the mind is not purely creative, in the sense that it paints pictures on the windows and then mistakes them for a landscape outside. But the mind is active, and its activity consists in following, so far as the will chooses to follow, the light outside that does really shine upon real landscapes. That is what gives the indefinably virile and even adventurous quality to this view of life; as compared with that which holds that material inferences pour in upon an utterly helpless mind, or that which holds that psychological influences pour out and create an entirely baseless phantasmagoria. In other words, the essence of the Thomist common sense is that two agencies are at work; reality and the recognition of reality; and their meeting is a sort of marriage. Indeed it is very truly a marriage, because it is fruitful; the only philosophy now in the world that really is fruitful. It produces practical results, precisely because it is the combination of an adventurous mind and a strange fact.
M. Maritain has used an admirable metaphor, in his book Theonas, when he says that the external fact fertilises the internal intelligence, as the bee fertilises the flower. Anyhow, upon that marriage, or whatever it may be called, the whole system of St. Thomas is founded; God made Man so that he was capable of coming in contact with reality; and those whom God hath joined, let no man put asunder
~G.K. Chesterton: St. Thomas Aquinas, VIII.