...wheresoever the earth may be placed, or whithersoever it may be carried by its animal faculty, heavy bodies will always be carried towards it. - Johannes Kepler

There are, in fact, as I began to say above, not a few principles which are the special property of mathematics, such principles as are discovered by the common light of nature, require no demonstration, and which concern quantities primarily; then they are applied to other things, so far as the latter have something in common with quantities. Now there are more of these principles in mathematics than in the other theoretical sciences because of that very characteristic of the human understanding which seems to be such from the law of creation, that nothing can be known completely except quantities or by quantities. And so it happens that the conclusions of mathematics are most certain and indubitable.

Nu ne întrebăm în ce scop util cântă păsările, cântecul este bucuria lor de când au fost zămislite pentru cântat. La fel, n-ar trebui să ne întrebăm de ce spiritul omului se străduieşte să pătrundă secretele cerurilor. Diversitatea fenomenelor naturii e atât de mare, iar comorile ascunse în ceruri atât de bogate, tocmai pentru ca spiritul omului să nu fie nicicând lipsit de hrană proaspătă.

No operation of addition or subtraction gives rise to diversity, but all are equally related to their pair of Terms, or Elements.