Finally, if there be still persons who are not sufficiently persuaded of the existence of God and of the soul, by the reasons I have adduced, I am desirous that they should know that all the other propositions, of the truth of which they deem themselves perhaps more assured, as that we have a body, and that there exist stars and an earth, and such like, are less certain;

We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.

Certainty is the mark of the common-sense life: gracious uncertainty is the mark of the spiritual life. To be certain of God means that we are uncertain in all our ways, we do not know what a day may bring forth. This is generally said with a sigh of sadness, it should be rather an expression of breathless expectation. We are uncertain of the next step, but we are certain of God. Immediately we abandon to God, and do the duty that lies nearest, He packs our life with surprises all the time.

A man may have metaphysical certainty without having "faith", that is, without this certainty residing in his soul as a continuously active presence. But if metaphysical certainty suffices on doctrinal grounds, it is far from being sufficient on the spiritual plane, where it must be completed and brought to life by faith. Faith is nothing other than the adherence of our whole being to Truth, whether we have a direct intuition of this Truth or an indirect notion.

"Because we cannot discover God's throne in the sky with a radiotelescope or establish (for certain) that a beloved father or mother is still about in a more or less corporeal form, people assume that such ideas are "not true." I would rather say that they are not "true" enough, for these are conceptions of a kind that have accompanied human life from prehistoric times, and that still break through into consciousness at any provocation.

Modern man may assert that he can dispose with them, and he may bolster his opinion by insisting that there is no scientific evidence of their truth. Or he may even regret the loss of his convictions. But since we are dealing with invisible and unknowable things (for God is beyond human understanding, and there is no means of proving immortality), why should we bother about evidence? Even if we did not know by reason our need for salt in our food, we should nonetheless profit from its use. We might argue that the use of salt is a mere illusion of taste or a superstition; but it would still contribute to our well-being. Why, then, should we deprive ourselves of views that would prove helpful in crises and would give a meaning to our existence?

And how do we know that such ideas are not true? Many people would agree with me if I stated flatly that such ideas are probably illusions. What they fail to realize is that the denial is as impossible to "prove" as the assertion of religious belief. We are entirely free to choose which point of view we take; it will in any case be an arbitrary decision.

There is, however, a strong empirical reason why we should cultivate thoughts that can never be proved. It is that they are known to be useful. Man positively needs general ideas and convictions that will give a meaning to his life and enable him to find a place for himself in the universe. He can stand the most incredible hardships when he is convinced that they make sense; he is crushed when, on top of all his misfortunes, he has to admit t

Permit me, sir, to give you one piece of advice. Be not so positive; especially with regard to things which are neither easy nor necessary to be determined. When I was young I was sure of everything. In a few years, having been mistaken a thousand times, I was not half so sure of most things as I was before. At present, I am hardly sure of anything but what God has revealed to man.

What can be more discouraging to a man than to doubt if his soul be material, like a stone or a reptile, and subject to corruption like the vilest creatures ? And does it not prove much more strength of mind and grandeur to be able to conceive the idea of a Being superior to all other beings, by whom and for whom all things were made; of a Being absolutely perfect and pure, without beginning or end, of whom our soul is the image, and of whom, if I may say so, it is a part, because it is spiritual and immortal?

I can't be sure God does not exist... On a scale of seven, where one means I know he exists, and seven I know he doesn't, I call myself a six... That doesn't mean I'm absolutely confident, that I absolutely know, because I don't.

Though we are certain of many things, yet that Certainty is no absolute Infallibility; there still remains the possibility of our being mistaken in all matters of humane Belief and Inquiry.

How could you comprehend things whose existence you doubt?

On the two kinds of certainty of eternal life. In this life there are two kinds of certainty concerning the life which is eternal: the one consists in those occasions when God tells us of it either himself or through an angel or special revelation, although this happens rarely and only to a few. The other kind of knowledge is better and more beneficial and falls frequently to those whose love is perfect. This happens to those whose love for and intimacy with their God is so great that they trust him completely and are so sure of him that they can no longer have any doubts, their certainty being founded on their love for him in all creatures without distinction. And if all creatures were to reject and abjure him, even if God himself were to do so, then they would not cease to trust, for love is not capable of mistrust but can only trust all that is good. And there is no need for anything to be said to either the lover or the beloved, for as soon as God senses that this person is his friend, he immediately knows all that is good for them and that belongs to their well-being. For however devoted you are to him, you may be sure that he is immeasurably more devoted to you and has incomparably more faith in you. For he is faithfulness itself – of this we can be certain as those who love him are certain. This type of certainty is far greater, more perfect and true than the other and it cannot deceive us, while the first kind can be deceptive and can easily be an illusion. Indeed, the second type is experienced in all the faculties of our soul and cannot deceive those who truly love God; indeed they no more doubt it than they doubt God himself, for love drives out all fear. ‘Love knows no fear’ as St John12 (1 John 4:18) says, and it is also written: ‘Love covers a multitude of sins’ (1 Peter 4:8). For where there is sin, there can be neither complete trust nor love, since love completely covers over sins and knows nothing of them. Not in such a way as if we had not sinned,

[L]et no one expect anything in the way of certainty of astronomy, since astronomy can offer us nothing certain, lest, if anyone take as true that which has been constructed for another use, he go away from this discipline a bigger fool than when he came to it.” Certainty could be found only in religion.

Religious people often say that religion offers absolute certainty about right and wrong; "god tells them" what it is. Even supposing that the aforementioned gods exist, and that the believers really know what the gods think, that still does not provide certainty, because any being no matter how powerful can still be wrong. Whether gods exist or not, there is no way to get absolute certainty about ethics. Without absolute certainty, what do we do? We do the best we can. Injustice is happening now; suffering is happening now. We have choices to make now. To insist on absolute certainty before starting to apply ethics to life decisions is a way of choosing to be amoral.