Augustine: Enchiridion, Chapter 20
Nor do I now undertake to solve a very knotty question, which perplexed those very acute thinkers, the Academic philosophers: whether a wise man ought to give his assent to anything, seeing that he may fall into error by assenting to falsehood: for all things, as they assert, are either unknown or uncertain. Now I wrote three volumes shortly after my conversion, to remove out of my way the objections which lie, as it were, on the very threshold of faith. And assuredly it was necessary at the very outset to remove this utter despair of reaching truth, which seems to be strengthened by the arguments of these philosophers. Now in their eyes every error is regarded as a sin, and they think that error can only be avoided by entirely suspending belief. For they say that the man who assents to what is uncertain falls into error; and they strive by the most acute, but most audacious arguments, to show that, even though a man’s opinion should by chance be true, yet that there is no certainty of its truth, owing to the impossibility of distinguishing truth from falsehood. But with us, “the just shall live by faith.” Now, if assent be taken away, faith goes too; for without assent there can be no belief. And there are truths, whether we know them or not, which must be believed if we would attain to a happy life, that is, to eternal life. But I am not sure whether one ought to argue with men who not only do not know that there is an eternal life before them, but do not know whether they are living at the present moment; nay, say that they do not know what it is impossible they can be ignorant of. For it is impossible that any one should be ignorant that he is alive, seeing that if he be not alive it is impossible for him to be ignorant; for not knowledge merely, but ignorance too, can be an attribute only of the living. But, forsooth, they think that by not acknowledging that they are alive they avoid error, when even their very error proves that they are alive, since one who is not alive cannot err. As, then, it is not only true, but certain, that we are alive, so there are many other things both true and certain; and God forbid that it should ever be called wisdom, and not the height of folly, to refuse assent to these.