99. Definition of Science. -- Science may be defined: A grouping of evident and certain, necessary and universal, systematically organized propositions, which are drawn immediately or mediately from the nature of the subject, and give the intrinsic reason of its properties and of the laws of its action. The propositions of a science must be:

(1) Objectively evident, i. e., manifestly true.

(2) Certain. An object of faith is, by definition, formally inevident; it is not, as such, an object of science. Scientific certitude is the outcome of systematic thought.

(3) Necessary and universal. To gather particular facts is not the work of science; at most it is preparatory to it. The man of science seeks to know what things are independently of their contingent and variable circumstances -- what is the law of their action. "There is no science but the universal", is Aristotle's favorite theme.

(4) Systematic, organized. Science is a unified whole. The unity of science, considered formally, consists in this: that its first definitions lay down the principles from which, by synthesis, all the following propositions are deduced. These generating principles are based upon the formal object of the particular science. That object is, if not the essence, at least a natural property, of a real subject. Consequently, the intimate reason of the unity of the science is the essence, the nature, of its object. This unity is the ideal of a perfect science.