Reason & Faith: Double-Truths?

Averroes, the prominent Islamic philosopher who said "I necessarily conclude through reason that the intellect is one in number; but I firmly hold the opposite through faith," thought that scientific truths are completely separate from and can even contradict truths not based on human reason, such as truths divinely revealed. This would seem to give science more academic freedom, being apparently unencumbered by seemingly unnecessary religious dogma. But the Islamic philosophy's decoupling of reason from religion and upholding a "double-truth" is a false philosophy with dangerous, irrational consequences, e.g., radical fundamentalism. However, science and the Catholic faith are compatible, as St. Thomas Aquinas's writings, the basis of Catholic philosophy, establish. In his De Unitate Intellectus Contra Averroistas ("On the Unity of the Intellect Against the Averroists"), the thirteenth-century St. Thomas refutes Averroes's denial of the individuality of the human intellect:

Just as all men naturally desire to know the truth [Aristotle, Metaphysics I, 1, 980a], so there is inherent in men a natural desire to avoid errors, and refute them when they are able to do so. Now among other errors, the error that seems especially inappropriate is the one concerning that very intellect through which we are meant by nature to avoid errors and know the truth. For a long time now there has been spreading among many people an error concerning the intellect, arising from the words of Averroes. He tries to assert that the intellect that Aristotle calls the possible intellect [Aristotle, De Anima III, 4, 429a 18-24], but that he himself calls by the unsuitable name "material," is a substance separate in its being from the body and not united to it in some way as its form, and furthermore that this possible intellect is one for all men. Against these views we have already written many things in the past [e.g., Summa Theologiae I, q. 76, a. 1 & 2]. But because the boldness of those who err has not ceased to strive against the truth, we will try again to write something against this same error to refute it clearly. It is not now our intention to show that the above-mentioned position is erroneous in this, that it is opposed to the truth of the Christian Faith. For this can easily enough become evident to everyone. For if we deny to men a diversity of the intellect, which alone among the parts of the soul seems to be incorruptible and immortal, it follows that after death nothing of the souls of men would remain except that single substance of intellect; and so the recompense of rewards and punishments and also their diversity would be destroyed. However, we intend to show that the above-mentioned position is no less against the principles of philosophy than against the teachings of Faith. And because, so they say, the words of the Latins on this subject have no savor for some persons, but these men say that they follow the words of the Peripatetics, whose books on this subject they have never seen, except those of Aristotle who was the founder of the Peripatetic Sect; we shall show first that the above-mentioned position is entirely opposed to his words and meaning.

—De unitate intellectus, pr.

Nowhere can the Catholic faith contradict true science or vice versa, even though there have been many accusations: (1) that of the Galileo affair, which was due to the fact that, unlike Copernicus, Galileo asserted his theory as absolutely true and not simply as a scientific theory subject to possible error, or (2) that the Church disapproves of the scientific theory of biological evolution, which is untrue; for according to Denzinger's 1911 edition of his collection of Catholic dogma, Enchiridion Symbolorum et Definitionum, the First Vatican Council states:

1797 [The impossibility of opposition between faith and reason]. But, although faith is above reason, nevertheless, between faith and reason no true dissension can ever exist, since the same God, who reveals mysteries and infuses faith, has bestowed on the human soul the light of reason; moreover, God cannot deny Himself, nor ever contradict truth with truth. But, a vain appearance of such a contradiction arises chiefly from this, that either the dogmas of faith have not been understood and interpreted according to the mind of the Church, or deceitful opinions are considered as the determinations of reason. Therefore, "every assertion contrary to the truth illuminated by faith, we define to be altogether false" [Lateran Council V, see n. 738]. 1798 Further, the Church which, together with the apostolic duty of teaching, has received the command to guard the deposit of faith, has also, from divine Providence, the right and duty of proscribing "knowledge falsely so called" [1 Tim. 6:20], "lest anyone be cheated by philosophy and vain deceit" [cf. Col. 2:8; can. 2]. Wherefore, all faithful Christians not only are forbidden to defend opinions of this sort, which are known to be contrary to the teaching of faith, especially if they have been condemned by the Church, as the legitimate conclusions of science, but they shall be altogether bound to hold them rather as errors, which present a false appearance of truth. 1799 [The mutual assistance of faith and reason, and the just freedom of science]. And, not only can faith and reason never be at variance with one another, but they also bring mutual help to each other, since right reasoning demonstrates the basis of faith and, illumined by its light, perfects the knowledge of divine things, while faith frees and protects reason from errors and provides it with manifold knowledge. Wherefore, the Church is so far from objecting to the culture of the human arts and sciences, that it aids and promotes this cultivation in many ways. For, it is not ignorant of, nor does it despise the advantages flowing therefrom into human life; nay, it confesses that, just as they have come forth from "God, the Lord of knowledge" [1 Samuel 2:3], so, if rightly handled, they lead to God by the aid of His grace. And it (the Church) does not forbid disciplines of this kind, each in its own sphere, to use its own principles and its own method; but, although recognizing this freedom, it continually warns them not to fall into errors by opposition to divine doctrine, nor, having transgressed their own proper limits, to be busy with and to disturb those matters which belong to faith.

Before a scientist might judge this as the Church's apparently being threatened by science and desperately trying to keep it "in its place," note what St. Thomas Aquinas says:

[T]he argument from authority based on human reason is the weakest, yet the argument from authority based on divine revelation is the strongest.

—Summa Theologica Iª q. 1 a. 8 ad 2

It would seem this is untrue because correct interpretation of divine revelation is difficult and subject to human error and speculation. But that human reason is subject to error is precisely the point; authority based on human reason is like building a house on sand. Compared to divine authority—authority based on the solid foundation of something most perfect, powerful, and immutable, i.e., absolute truth itself—human reason is unstable, changing, fleeting, and restrained by time. Therefore, "the argument from authority based on divine revelation is [indeed] the strongest;" and consequently science, with its roots in a true philosophy (i.e., Scholastic Thomism) that does not contradict divine revelation nor human reason but strives to understand a single absolute truth, is even stronger. This is true science.