How often must I repeat, that I know or am conscious of my own being; and that I myself am not my ideas, but somewhat else, a thinking, active principle that perceives, knows, wills, and operates about ideas?

That the discovery of this great truth, which lies so near and obvious to the mind, should be attained to by the reason of so veryfew, is a sad instance of the stupidity and inattention of men, who, though they are surrounded with such clear manifestations of the Deity, are yet so little affected by them, that they seem as it were blinded with excess of light.

But the velocities of the velocities - the second, third, fourth, and fifth velocities, etc. - exceed, if I mistake not, all human understanding.

Our youth we can have but to-day, We may always find time to grow old.

Many things, for aught I know, may exist, whereof neither I nor any other man hath or can have any idea or notion whatsoever.

The same principles which at first view lead to skepticism, pursued to a certain point, bring men back to common sense.

In short, if there were external bodies, it is impossible we should ever come to know it; and if there were not, we might have the very same reasons to think there were that we have now.