Courteous Reader,

I do ingenuously confess, that both for want of learning and reading philosophical authors, I have not expressed myself in my philosophical works, especially in my Philosophical and Physical Opinions, so clearly and plainly as I might have done, had I had the assistance of art, and the practice of reading other authors: But though my conceptions seem not so perspicuous in the mentioned book of philosophical opinions; yet my Philosophical Letters, and these present Observations, will, I hope, render it more intelligible: which I have writ, not out of an ambitious humour, to fill the world with useless books, but to explain and illustrate my own opinions. For, what benefit would it be to me, if I should put forth a work, which by reason of its obscure and hard notions, could not be understood? especially it being well known, that natural philosophy is the hardest of all human learning, by reason it consists only in contemplation; and to make the philosophical conceptions of one's mind known to others, is more difficult than to make them believe, that if A. B. be equal to C. D. then E. F. is equal to A. B. because it is equal to C. D.