Vitae philosophorum

A coupled proposition is one which is put together by certain coupling conjunctions, e.g. It is day-time and it is light. A disjunctive proposition is one which is constituted such by the disjunctive conjunction Either, as e.g. Either it is day or it is night. This conjunction guarantees that one or other of the alternatives is false. A causal proposition is constructed by means of the conjunction Because, e.g. Because it is day, it is light. For the first clause is, as it were, the cause of the second. A proposition which indicates more or less is one that is formed by the word signifying rather and the word than in between the clauses, as, for example, It is rather day-time than night.

Opposite in character to the foregoing is a proposition which declares what is less the fact, as e.g. It is less or not so much night as day. Further, among propositions there are some which in respect of truth and falsehood stand opposed to one another, of which the one is the negative of the other, as e.g. the propositions It is day and It is not day. A hypothetical proposition is therefore true, if the contradictory of its conclusion is incompatible with its premiss, e.g. If it is day, it is light. This is true. For the statement It is not light, contradicting the conclusion, is incompatible with the premiss It is day. On the other hand, a hypothetical

An inferential proposition is true if starting from a true premiss it also has a consequent conclusion, as e.g. Since it is day, the sun is above the horizon. But it is false if it starts from a false premiss or has an inconsequent conclusion, as e.g. Since it is night, Dion is walking, if this be said in day-time. A causal proposition is true if its conclusion really follows from a premiss itself true, though the premiss does not follow conversely from the conclusion, as e.g. Because it is day, it is light, where from the it is day the it is light duly follows, though from the statement it is light it would not follow that it is day. But a causal proposition is false if it either starts from a false premiss or has an inconsequent conclusion or has a premiss that does not correspond with the conclusion, as e.g. Because it is night, Dion is walking.

A probable judgement is one which induces to assent, e.g. Whoever gave birth to anything, is that thing’s mother. This, however, is not necessarily true; for the hen is not mother of an egg.

Again, some things are possible, others impossible; and some things are necessary, others are not necessary. A proposition is possible which admits of being true, there being nothing in external circumstances to prevent it being true, e.g. Diocles is alive. Impossible is one which does not admit of being true, as e.g. The earth flies. That is necessary which besides being true does not admit of being

A reasonable proposition is one which has to start with more chances of being true than not, e.g. I shall be alive to-morrow.

And there are other shades of difference in propositions and grades of transition from true to false— and conversions of their terms—which we now go on to describe broadly.

An argument, according to the followers of Crinis, consists of a major premiss, a minor premiss, and a conclusion, such as for example this: If it is day, it is light; but it is day, therefore it is light. Here the sentence If it is day, it is light is the major premiss, the clause it is day is the minor premiss, and therefore it is light is the conclusion. A mood is a sort of outline of an argument, like the following: If the first, then the second; but the first is, therefore the second is.