If a man will begin with certainties, he shall end in doubts, but if he will be content to begin with doubts, he shall end in certainties.

We delight in one knowable thing, which comprehends all that is knowable; in one apprehensible, which draws together all that can be apprehended; in a single being that includes all, above all in the one which is itself the all.

There is nothing certain except the unforeseen.

When we are not sure, we are alive.

The one unchangeable certainty is that nothing is unchangeable or certain.

A woman's guess is much more accurate than a man's certainty.

There is nothing certain in a man's life but that he must lose it.

Only one thing is certain -- that is, nothing is certain. If this statement is true, it is also false.

In these matters the only certainty is that there is nothing certain.

Certainties are arrived at only on foot.

There is nothing certain, but the uncertain.

If you have a choice between certainty and hope, choose certainty every time.

I tore myself away from the safe comfort of certainties through my love for truth; and truth rewarded me.

He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an unhappy man, for he has put a knife in the heart of wonder.

The best lack all conviction, while the worst are full of passionate intensity.