A Vulgar Mechanick can practice what he has been taught or seen done, but if he is in an error he knows not how to find it out and correct it, and if you put him out of his road he is at a stand. Whereas he that is able to reason nimbly and judiciously about figure, force, and motion, is never at rest till he gets over every rub. (from a letter dated 25 May, 1694)

In the absence of any other proof, the thumb alone would convince me of God's existence.

I see I have made my self a slave to Philosophy.

Thus this Earth resembles a great animall or rather an inanimate vegetable, draws in aethereal breath for its dayly refreshment and vitall ferment and transpires again grosses exhalations. And, according to the condition of all other things living, ought to have its time of beginning, youth, old age and perishing.

[1.] And first I suppose that there is diffused through all places an aethereal substance capable of contraction & dilatation, strongly elastick, & in a word, much like air in all respects, but far more subtile. 2. I suppose this aether pervades all gross bodies, but yet so as to stand rarer in their pores then in free spaces, & so much ye rarer as their pores are less ... 3. I suppose ye rarer aether within bodies & ye denser without them, not to be terminated in a mathematical superficies, but to grow gradually into one another.

I can measure the motion of bodies but I cannot measure human folly.

If I have ever made any valuable discoveries, it has been due more to patient attention, than to any other talent