No wonder true metaphysicians are rare. Common sense does not rise above the level of imaginable realities, and , when it is a question of metaphysics, the vulgus includes many a mind eminent in other fields. Scientists, artists of genius, great statesmen–all those who like to proclaim: “I only know what I can see and touch,” even though in other respects they may be eminent specimens of the human kind, are nevertheless unfit for metaphysical speculation. Let us add, for their consolation, that they are perfectly normal men. Anyone who says, “I understand nothing of what you call metaphysics,” is quite justified, and there is for him nothing to feel ashamed of. But he should stop there. That one does not see any light, may be a fact; to infer from it that there is no light, is a non sequitur.
–Etienne Gilson, The Spirt of Thomism, 1964
Peripatetic Praxis 