In accordance with that experience which directs to the profoundest books for the simplest statements, we turn to Mill's Logic for the philosophy of propositions. The answer to every question which it is possible to frame is contained in a proposition or assertion. Whatever can be an object of belief or even of disbelief, must, when put into words, assume the form of a proposition * * What we call a truth is simply a true proposition; and errors are false propositions. To know the import of all possible propositions would be to know all questions which can be raised, all matters which are susceptible of being either believed or disbelieved. * * Since then the objects of all belief and all inquiry express themselves in propositions, a sufficient scrutiny of propositions and of their varieties will apprise us what questions mankind have asked themselves, and what it the nature of the answers to those questions they have actually thought they had grounds to believe.

'Now the first glance at a proposition shows that it is formed by putting together two names. A proposition, according to the common simple definition, which is sufficient for our purpose, is, discourse in which something is affirmed or denied of something. Thus, in the proposition, gold is yellow, the quality yellow is affirmed of the substance gold. In the proposition, Franklin was not born in England, the fact expressed by the words born in England is denied of the man Franklin.

'Every proposition consists of three parts: the subject, the predicate, and the copula. The predicate is the name denoting that which is affirmed or denied. The subject is the name denoting the person or thing which something is affirmed or denied of. The copula is the sign denoting that there is an affirmation or denial; and thereby enabling the hearer or reader to distinguish a proposition from any other kind of discourse. Thus, in the proposition, the earth is round, the predicate is the word round, which denotes the quality affirmed, or (as the phrase is) predicated: the earth words denoting the object which that quality is affirmed of, compose the subject; the word it, which serves as the connecting mark between the subject and predicate, to show that one of them is affirmed of the other, is called the copula.'