Sacred Demonstrations, or the Christian Euclid, Book II

Because it is hard for the truth to appear anywhere among so many diverse men and cultures on account of the equal authority of the same deity everywhere, but mere credulity persuades all things and for the most part imposes upon the rude, while it restrains the prudent. I shall clearly imitate the method of Euclid, the prince of geometers, although my elements are for the most part from a posterior notion, that is, from nature more than from what is familiar to us, whereas his principles immediately either move one to assent or take away the ability to deal with those who hold that assent should be withheld from them. I shall have this in common with Euclid and the authors of all disciplines: that one should not act against one who denies principles, unless perhaps he contradicts himself. For then it will be possible to act against him in such a way as to show that the things he asserts against the truth are false. Truly, the things I am going to write in the first place are most common and everywhere obvious, and I shall take up nothing removed from common use, but having applied those things through which one can come to the knowledge of the truth, I shall inquire in the peripatetic manner whether it exists, what it is, to what ends, and from whom it is. Then, from the things conceded, I shall attempt to lead the mind to a greater light of truth. But because it is already agreed that it is not for the students of philosophy to call the things themselves into question whether they exist, unless some obscurity compels one to doubt, but rather, having first placed certain things which no one would deny exist, I shall come through their definitions to their offices, properties, and ends, having applied numbers in the first position, so that in the following inductions we can confirm our intentions with the applied number without repetition of words. First, although the cause and the principle ought to be prior in writing, as they are in nature, than the effects,