2. It is knowledge when anything is known with definiteness; opinion, when a thing lurks as yet in uncertainty and seems in no way established, as for example, whether the sun is [only] as large as it seems or greater than all the earth; likewise whether the moon is a sphere or concave; and whether the stars adhere to the heavens or pass in free course through the air; of what size the heaven itself is and of what material it is composed; whether it is quiet and motionless or revolves with incredible speed; how great is the thickness of the earth, or on what foundations it continues poised and supported. 3. The word philosophy, translated into Latin, means _amor sapientiae_. For the Greeks call amor φιλὸν, and sapientiae σοφίαν. The sub-division of philosophy is three-fold: first, natural philosophy, which in Greek is called _physica_, in which there is discussion of the search into nature; the second, moral, which in Greek is called _ethica_, in which the subject is morals; the third, rational, which in the Greek is called _logica_, in which the discussion is as to how the truth itself is to be sought in respect to the causes of things or the conduct of life. 4. In physics, then, the cause of inquiry, in ethics, the manner of living, in logic, the method of understanding, are concerned. Among the Greeks, Thales of Miletus, one of the seven wise men, was the first to search into natural philosophy. For this man first regarded with contemplative thought the causes of the heavens and the force of the things of nature. And this division of philosophy Plato afterward divided into four separate parts, namely, into arithmetic, geometry, music, astronomy. 5. Socrates first established ethics with a view to correcting and ordering conduct, and he devoted all his attention to the discussion of right living, dividing it into the four virtues of the soul, namely, wisdom, justice, fortitude, temperance. 6. Wisdom is engaged with things, and by it the evil is distinguished from the good. Fortitude, by which adversity is endured with calmness. Temperance, by which lust and concupiscence are bridled. Justice, by which through righteous judgment his own is rendered to each. 7. Plato added logical philosophy, which is called rational, and by it he analyzed the causes of things and of conduct, and examined their force in a rational way, dividing it into dialectic and rhetoric. It is called logical, that is, rational, for among the Greeks λόγος means both word and reason. 8. The divine utterances also consist of these three kinds of philosophy. For they are wont to discuss nature, as in Genesis or Ecclesiastes; or conduct, as in Proverbs and here and there in all the books; or logic, instead of which our [philosophers] assert the claim of theology,[232] as in the Song of Songs or the Gospels. [232] Du Breul has _theologia_; Arevalus, _theorica_.