65. Conditions of a Strictly Scientific Conclusion. -- Examining into the nature of the scientific demonstration, Aristotle determines its properties as follows:

The premises of the determinate syllogism must be true, primary, immediate, better known than the conclusion, anterior to it, and the cause or reason of its truth.

(1) True: Although false premises may sometimes be followed by a true conclusion (57), falsity as such is never the origin of a truth. The aim of the demonstration being to bring a true conclusion out of the premises, a good demonstration must proceed from true premises, the natural source of truth.

(2) Primary -- themselves incapable of demonstration -- in the sense that all the demonstrations of a science should form a single chain, the first link of which is formed out of premises that cannot be demonstrated. Hence, in relation to those which follow them, these primary premises are:

(3) Immediate, i. e., evident without need of demonstration.

(4) The cause or reason^{1} of the conclusion, not only in the logical order of our knowledge, but in the ontological order.

(5) Anterior to the conclusion, since the premises must contain the cause or reason of the conclusion. This anteriority may be only a priority of nature.

(6) Better known than the conclusion, the aim of reasoning being to effect a passage from what is better known to what is less, or not at all, known. Observe that this Aristotelean theory refers to the ontological order. In our subjective point of view the sensible fact precedes the abstract quiddity which we separate from it; the particular leads to the universal. But in reality nature is prior to its sensible manifestations, the law is the reason why the fact is, and is necessary to its explanation.

{1} On this distinction see General Metaphysics, no. 165.