St. Thomas Aquinas on faith and doubt

More on one of my favorite themes, the incompatibility of faith and doubt (see previous posts here, here and here):

Faith implies assent of the intellect to that which is believed. Now the intellect assents to a thing in two ways. First, through being moved to assent by its very object, which is known either by itself (as in the case of first principles, which are held by the habit of understanding), or through something else already known (as in the case of conclusions which are held by the habit of science). Secondly the intellect assents to something, not through being sufficiently moved to this assent by its proper object, but through an act of choice, whereby it turns voluntarily to one side rather than to the other: and if this be accompanied by doubt or fear of the opposite side, there will be opinion, while, if there be certainty and no fear of the other side, there will be faith.

S.T., II-II, Q. 1, A. 4.

Thus St. Thomas, like Cardinal Newman, clearly pits doubt against faith: When doubt persists, then all one has is opinion; whereas when authentic faith is present there is certainty.

Because science [1] is incompatible with opinion about the same object simply, for the reason that science demands that its object should be deemed impossible to be otherwise, whereas it is essential to opinion, that its object should be deemed possible to be otherwise. Yet that which is the object of faith, on account of the certainty of faith, is also deemed impossible to be otherwise; and the reason why science and faith cannot be about the same object and in the same respect is because the object of science is something seen whereas the object of faith is the unseen, as stated above.

S.T., II-II, Q. 1, A. 5, Ad. 4.

Thus according to St. Thomas, science and faith are equally certain, the difference being that science is certain about things that it sees, whereas faith is certain about what is unseen (cf. Heb. 11:1): “Now those things are said to be seen which, of themselves, move the intellect or the senses to knowledge of them. Wherefore it is evident that neither faith nor opinion can be of things seen either by the senses or by the intellect.”

[1] “Science [in this context] is not taken in the restricted meaning of natural sciences, but in the general one given to the word by Aristotle and St. Thomas Aquinas. Aristotle defines science as a sure and evident knowledge obtained from demonstrations. This is identical with St. Thomas’s definition of science as the knowledge of things from their causes.” New Advent Catholic Encyclopedia, article on “Science and the Church”


6 thoughts on “St. Thomas Aquinas on faith and doubt

  1. Pingback: The glorification of doubt | Agellius's Blog

  2. Faith is about things that can’t be seen, but aren’t some aspects of faith, like belief in the resurrection, about things that are historical, and could have been seen at one point in time?


  3. Yes, the Resurrection is a historical fact and may be investigated and assented to as such. Belief in the occurrence of the Resurrection as a result of historical investigation would not be a matter of faith but of science, like any other historical event. What is a matter of faith, is the significance and meaning of the Resurrection, the fact that thereby Jesus broke the bonds of death and opened the gates of Heaven for those who believe in him, and so forth. I would say that the Resurrection can also be a matter of faith, in that people who don’t have the means or the ability to investigate the facts for themselves, can put their faith in it nevertheless, as a result of its being taught by the Church.


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  6. Pingback: The blessing of not seeing and yet believing | Petty Armchair Popery

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