But possibly the definition of a philosopher may exempt us from the perplexities to which the ambiguous expressions of common writers expose us. I therefore thought fit to consider, with a somewhat more than ordinary attention, the famous definition of nature that is left us by Aristotle, which I shall recite rather in Latin than in English – not only because it is very familiarly known among scholars in that language, but because there is somewhat in it that (I confess) seems difficult to me to be without circumlocution rendered intelligibly in English: Natura, says he, est principium et causa motus et quietis ejus, in quo inest, primo per se, et non secundum accidens, [Nature is the principle and cause of movement and rest in the thing to which it belongs primarily, in virtue of itself, and not contingently.] But though, when I considered that according to Aristotle the whole world is but a system of the works of nature, I thought it might well be expected that the definition of a thing, the most important in natural philosophy, should be clearly and accurately delivered.

Yet to me, this celebrated definition seemed so dark, that I cannot brag of any assistance I received from it towards the framing of a clear and satisfactory notion of nature. For I dare not hope, that what as to me is not itself intelligible should make me understand what is to be declared or explicated by it.