The best and safest way of philosophising seems to be, first to enquire diligently into the properties of things, and to establish those properties by experiences [experiments] and then to proceed slowly to hypotheses for the explanation of them. For hypotheses should be employed only in explaining the properties of things, but not assumed in determining them; unless so far as they may furnish experiments.

You ask me how, with so much study, I manage to retene my health. Morpheus is my last companion; without 8 or 9 hours of him yr correspondent is not worth one scavenger's peruke. My practices did at ye first hurt my stomach, but now I eat heartily enou' as y' will see when I come down beside you.

The Ignis Fatuus is a vapor shining without heat.

Every body persists in a state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces having impact upon it.

Plato is my friend, Aristotle is my friend, but my greatest friend is truth.

Whence arises all that order and beauty we see in the world?

Against filling the Heavens with fluid Mediums, unless they be exceeding rare, a great Objection arises from the regular and very lasting Motions of the Planets and Comets in all manner of Courses through the Heavens.