§ 203. We may notice, however, in passing, that truth and falsehood
are attributes of propositions and of propositions only. For something
must be predicated, i.e. asserted or denied, before we can have
either truth or falsehood. Neither concepts or terms, on the one hand,
nor reasonings, on the other, can properly be said to be true or
false. In the mere notion of a Centaur or of a black swan there is
neither truth nor falsehood; it is not until we make some statement
about these things, such as that 'black swans are found in Australia,'
or 'I met a Centaur in the High Street yesterday,' that the question
of truth or falsehood comes in. In such expressions as a 'true friend'
or 'a false patriot' there is a tacit reference to propositions. We
mean persons of whom the terms 'friend' and 'patriot' are truly or
falsely predicated. Neither can we with any propriety talk of true or
false reasoning. Reasoning is either valid or invalid: it is only the
premisses of our reasonings, which are propositions, that can be true
or false. We may have a perfectly valid process of reasoning which
starts from a false assumption and lands us in a false conclusion.
§ 204. All truth and falsehood then are contained in propositions; and
propositions are divided according to the Quality of the Matter into
true and false. But the consideration of the matter is outside the
sphere of formal or deductive Logic. It is the problem of inductive
logic to establish, if possible, a criterion of evidence whereby the
truth or falsehood of propositions may be judged (§ 2).
§ 205. Another usual division of propositions is into Pure and Modal,
the latter being those in which the copula is modified by some degree
of probability. This division is excluded by the view which has just
been taken of the copula, as being always simply affirmative or simply
negative.
§ 206. We are left then with the following divisions of
propositions--
Proposition
according to Form
Simple
Complex
Conjunctive
Disjunctive
Universal
Singular
General
according to Matter
Verbal
Real
according to Quantity
Universal
Singular
General
Particular
Indefinite
(strictly) Particular
according to Quality
Affirmative
Negative
_Simple and Complex Propositions_.
§ 207. A Simple Proposition is one in which a predicate is directly
affirmed or denied of a subject, e.g. 'Rain is falling.'
§ 208. A simple proposition is otherwise known as Categorical.
§ 209. A Complex Proposition is one in which a statement is made
subject to some condition, e.g. 'If the wind drops, rain will fall.'
§ 210. Hence the complex proposition is also known as Conditional.
§ 211. Every complex proposition consists of two parts--
(1) Antecedent;
(2) Consequent.
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