GENERAL experiential Truths, such as we have just spoken of, are called _Theories_, and the particular observations from which they are collected, and which they include and explain, are called _Facts_. Thus Hipparchus's doctrine, that the sun moves in an eccentric about the earth, is _his Theory_ of the Sun, or the _Eccentric Theory_. The doctrine of Kepler, that the Earth moves in an Ellipse about the Sun, is _Kepler's Theory_ of the Earth, the Elliptical Theory. Newton's doctrine that this elliptical motion of the Earth about the Sun is produced and governed by the Sun's attraction upon the Earth, is the _Newtonian_ theory, the _Theory of Attraction_. Each of these Theories was accepted, because it included, connected and explained the _Facts_; the Facts being, in the two former cases, the motions of the Sun as observed; and in the other case, the elliptical motion of the Earth as known by Kepler's Theory. This antithesis of _Theory_ and _Fact_ is included in what has just been said of Inductive Propositions. A Theory is an Inductive Proposition, and the Facts {30} are the particular observations from which, as I have said, such Propositions are inferred by Induction. The Antithesis of Theory and Fact implies the fundamental Antithesis of Thoughts and Things; for a Theory (that is, a true Theory) may be described as a Thought which is contemplated distinct from Things and seen to agree with them; while a Fact is a combination of our Thoughts with Things in so complete agreement that we do not regard them as separate. Thus the antithesis of Theory and Fact involves the antithesis of Thoughts and Things, but is not identical with it. Facts involve Thoughts, for we know Facts only by thinking about them. The Fact that the year consists of 365 days; the Fact that the month consists of 30 days, cannot be known to us, except we have the Thoughts of Time, Number and Recurrence. But these Thoughts are so familiar, that we have the fact in our mind as a simple Thing without attending to the Thought which it involves. When we mould our Thoughts into a Theory, we consider the thought as distinct from the Facts; but yet, though distinct, not independent of them; for it is a true Theory, only by including and agreeing with the Facts. _Sect._ 5.--_Ideas and Sensations._