It may be asked: Seeing that St Thomas is so often at fault in matter where his doctrines have come under the test of modern experimental science and criticism, what confidence can be reposed in him on other points, where his conclusions lie beyond the reach of experience? To a Catholic the answer is simple enough; and it shall be given in St Thomas's own words: "Our faith reposes on the revelation made to the Apostles and Prophets who have written the Canonical Books, not on any revelation that may have been made to other Doctors" (Sum. Theol. I, q. 8 ad 2, -- the context is worth reading). Our confidence is limited in conclusions of mere reason, by whomsoever drawn: our confidence is unlimited in matters of faith, as taught by the Church (B. I, Chapp. III-VI). The practical value of the Summa contra Gentiles lies in its exposition of the origin, nature, duty, and destiny of man, according to the scheme of Catholic Christianity. That scheme stands whole and entire in the twentieth century as it stood in the thirteenth: in that, there is nothing to alter in the Contra Gentiles: it is as practical a book as ever it was. The débris are the débris of now worn-out human learning, which St Thomas used as the best procurable in his day, to encase and protect the structure of faith. Or, to express myself in terms of the philosophy of our day, dogma has not changed, but our 'apperception' of it, or the 'mental system' into which we receive it. So the Summa contra Gentiles stands, like the contemporary edifices of Ely and Lincoln: it stands, and it will stand, because it was built by a Saint and a man of genius on the rock of faith.
The Summa contra Gentiles is an historical monument of the first importance for the history of philosophy. In the variety of its contents, it is a perfect encyclopaedia of the learning of the day. By it we can fix the high water mark of thirteenth-century thought: -- for it contains the lectures of a Doctor second to none in the greatest school of thought then flourishing, the University of Paris. It is by the study of such books that one enters into the mental life of the period at which they were written; not by the hasty perusal of Histories of Philosophy. No student of the Contra Gentiles is likely to acquiesce in the statement, that the Middle Ages were a time when mankind seemed to have lost the power of thinking for themselves. Mediaeval people thought for themselves, thoughts curiously different from ours, and profitable for us to study.
Lastly, the Summa contra Gentiles is mega tekmêrion -- considering the ravages of six and a half centuries of time upon what was once the most harmonious blending of faith with the science of the day, -- it is a fact of solemn admonition to all Doctors and Professors of Philosophy and Theology within the Church of Christ, that they should be at least as solicitous as an English Dean and Chapter now are, for the keeping in yearly repair of the great edifice given over to their custody; that they should regard with watchful and intelligent eyes the advance of history, anthropology, criticism and physical science; and that in their own special sciences they should welcome, and make every sane endeavour to promote, what since 1845 has been known as the Development of Doctrine.
4.97 : Of the State of the World after the judgement