We know the truth not only through our reason but also through our heart. It is through the latter that we know first principles, and reason, which has nothing to do with it, tries in vain to refute them.

Certainly the Church does not condemn the efforts of those who want to know the truth, since it is God who made it the nature of man to be most eager to grasp truth. Nor does she condemn the efforts of healthy and right reason, for it is through this reason that we cultivate the spirit, study nature, and bring to light its most hidden secrets. This tender mother recognizes and justly maintains that reason is the most notable of the heavenly gifts, since it is through reason that we raise ourselves above the senses and display a certain image of God in ourselves.

When we find out an Idea, by whose Intervention we discover the Connexion of two others, this is a Revelation from God to us, by the voice of Reason.

Reason is a light that God has kindled in the soul

The word of God is God, and therefore has to be revealed to you by God. When God’s Holy Spirit reveals to you the meaning of His word, then you will recognize the truth of His word.

The revelation of God, in which man's fulfilment of the true knowledge of God takes place, is the disposition of God in which He acts towards us as the same triune God that He is in Himself, and in such a way that, although we are men and not God, we receive a share in the truth of His knowledge of Himself. Certainly it is the share which He thinks proper and which is therefore suitable for us. But in this share we have the reality of the true knowledge of Himself.

Revelation may not need the help of reason, but man does, even when in possession of revelation. Reason may be described as the candle in the man's hand, to which revelation brings the necessary flame.

A revelation, that may be supposed to be really of the institution of God, must also be supposed to be perfectly consistent or uniform, and to be able to stand the test of truth; therefore such pretended revelations, as are tendered to us as the contrivance of heaven, which do not bear that test, we may be morally certain, was either originally a deception, or has since, by adulteration become spurious. Reason therefore must be the standard by which we determine the respective claims of revelation; for otherwise we may as well subscribe to the divinity of the one as of the other, or to the whole of them, or to none at all.

Reason is God's gift; but so are the passions.

Reason alone cannot prove the existence of God. Faith is reason plus revelation, and the revelation part requires one to think with the spirit as well as with the mind. You have to hear the music, not just read the notes on the page.

Reason, in fact, is a thing of God, inasmuch as there is nothing which God the Maker of all has not provided, disposed, ordained by reason — nothing which He has not willed should be handled and understood by reason. All, therefore, who are ignorant of God, must necessarily be ignorant also of a thing which is His, because no treasure-house at all is accessible to strangers. And thus, voyaging all the universal course of life without the rudder of reason, they know not how to shun the hurricane which is impending over the world.

Truth is the courage to fathom the facts in order to see how they relate to the Word.

Truth is the agreement of our ideas with the ideas of God.

It is a step to have it proved, that there must be something in the world more than what we see. It is a further step to know, that, amongst the invisible things of nature, there must be an intelligent mind, concerned in its production, order, and support. These points being assured to us by Natural Theology, we may well leave to Revelation the disclosure of many particulars, which our researches cannot reach, respecting either the nature of this Being as the original cause of all things, or his character and designs as a moral governor ; and not only so, but the more full confirmation of other particulars, of which, though they do not lie altogether beyond our reasonings and our probabilities, the certainty is by no means equal to the importance. The true theist will be the first to listen to any credible communication of Divine knowledge. Nothing which he has learned from Natural Theology, will diminish his desire of further instruction, or his disposition to receive it with humility and thankfulness. He wishes for light: he rejoices in light. His inward veneration of this great Being, will incline him to attend with the utmost seriousness, not only to all that can be discovered concerning him by researches into nature, but to all that is taught by a revelation, which gives reasonable proof of having proceeded from him.