Pasteur's faith was as genuine as his science. In his panegyric of Littré, whose fauteuil he took, he said:Happy the man who bears within him a divinity, an ideal of beauty and obeys it; and ideal of art, and ideal of science, an ideal of country, and ideal of the virtues of the Gospel.These words are graven above his tomb in the Institut Pasteur. In his address Pasteur said further "These are the living springs of great thoughts and great actions. Everything grows clear in the reflections from the Infinite". Some of his letters to his children breathe profound simple piety. He declared "The more I know, the more nearly is my faith that of the Breton peasant. Could I but know all I would have the faith of a Breton peasant woman." What he could not above all understand is the failure of scientists to recognize the demonstration of the existence of the Creator that there is in the world around us. He died with his rosary in his hand, after listening to the life of St. Vincent de Paul which he had asked to have read to him, because he thought that his work like that of St. Vincent would do much to save suffering children.
There is a great difference between Christian philosophy and human wisdom. The latter, guided solely by the light of nature, advances slowly by reasoning on sensible objects and effects, and only after long and laborious investigation is it able at length to contemplate with difficulty the invisible things of God, to discover and understand a First Cause and Author of all things. Christian philosophy, on the contrary, so quickens the human mind that without difficulty it pierces the heavens, and, illumined with divine light, contemplates first, the eternal source of light, and in its radiance all created things: so that we experience with the utmost pleasure of mind that we have been called, as the Prince of the Apostles says, out of darkness into his admirable light, and believing we rejoice with joy unspeakable. (1 Pet. 1:8; 1 Pet. 2:9)On today's sharp division into mutually exclusive "objective" and "subjective" realms of knowledge and natural reason versus religion, faith, or "supernatural reason," respectively, Werner Heisenberg said:
Justly, therefore, do the faithful profess first to believe in God, whose majesty, with the Prophet Jeremias, we declare incomprehensible (Jer. 32:19). For, as the Apostle says, He dwells in light inaccessible, which no man hath seen, nor can see (1 Tim. 6:16); as God Himself, speaking to Moses, said: No man shall see my face and live (Exod. 33:20). The mind cannot rise to the contemplation of the Deity, whom nothing approaches in sublimity, unless it be entirely disengaged from the senses, and of this in the present life we art naturally incapable.*
Summa Theol. Ia. xii. 11.
I have to admit that I do not feel happy about this division. I doubt whether any human society can in the long term live with this sharp division between knowledge and faith. [...] Then Wolfgang Pauli took up the thread of the discussion and agreed with Heisenberg's doubt, asserting in fact that this was quite certain: "The complete division between knowledge and faith is surely just a temporary stopgap measure. In western society and culture we could for instance, in the not-too-distant future, come to the point at which the parables and images that religion has used up to now are not longer convincing even for simple folk; and then, I fear, traditional morality will also very rapidly break down, and things will happen that are more frightful than anything we can yet imagine."Fortunately, faith and knowledge are not divided. Because all sciences ultimately point toward understanding God or "a First Cause and Author of all things"—and since God is "the truth," i.e., the absolute Truth (John 14:6)—St. Thomas Aquinas says:
—Pope Benedict XVI's Truth and Tolerance
We have a more perfect knowledge of God by grace than by natural reason. Which is proved thus. The knowledge which we have by natural reason contains two things: images derived from the sensible objects; and the natural intelligible light, enabling us to abstract from them intelligible conceptions. Now in both of these, human knowledge is assisted by the revelation of grace. For the intellect's natural light is strengthened by the infusion of gratuitous light.Kurt Gödel's seminal 1931 paper On Formally Undecidable Propositions of Principia Mathematica and Related Systems showed that there are true propositions within formal mathematical systems that can neither be proven true nor false within their respective system. The propositions require something beyond—a sort of "faith" or outside means—to justify their truth. Thus mathematics, an invention of the human intellect, has its limitations. Similarly, the finite human mind has its limitations without the light of Divine Assistance, too—especially when it comes to understanding the Infinite, let alone the physical world.
—Summa Theol. Ia. xii. 13, a comparison of faith and reason
It seems Pasteur, Heisenberg, Pauli, and Gödel all recognized the finitude of natural reason and its freedom to transcend when coupled with faith.