NECESSITY. This word occurs in connection with two different philosophical subjects, namely, the freedom of the will (see FREE-Wm.). and the nature of our belief in fundamental truths, such as the axioms of mathematics. It it alleged by some philosophers that the truths held by us as most certain are the result of experience, and that the degree of certainty is but a measure of the universality of the experience. Otherscontend that such first principles as the axioms of mathematics arc not only true, but veresmarily true, Such necessity, it is argued, cannot come from mere experience, and therefore implies an innate or intuitive source. Hence the theory of necessary truth is only another name for the theory of instinctive or intuitive truth.
Necessity is a word too vague in its signification to serve as a leading term in philoso phy. There are several meanings attaching to it which should be clearly set forth before entering on the discussion of such questions as those above mentioned.
1. Necessity, in the first place, means that one fact or statement is implied in another Thus, if we say that all the apostles were .Jews, it follows necessarily that Peter was a Jew; this is not a new fact, but merely a reassertion of a portion of the same fact. We are not at liberty to affirm a thing in one form, and then deny the same thing when ex pressed in a different form. If we say this room is hot, it is repeating the assertion in another way, to say that it is not cold. These truths follow by necessary inference. Hence the general axiom of the syllogism, that what is true of a whole class must be true of each individual, is a necessary truth in this sense. In affirming such a truth, we merely declare that we shall be consistent, and that when we have affirmed a proposition in company with other to affirm 'it When taken apart from the others This kind of necessity is sometimes Called logical necessity, and sometimes mathematical necessity. We might call it deductive necessity, or necessity by impli cation.
2. A second meaning is inductive certainty; or the certainty that arises from a well• grounded experience. That lead will sink in water; that animals need food and air in order to live; that warmth promotes vegetation,—are truths that we call necessary, in the sense of being so certain that we may always count upon them. We presume with the highest confidence, that an unsupported body will fall to the ground, not because the fact of falling is implied in the fact of matter, but because nature has uniformly conjoined the two Teets. We can speak even of moral necessity; by which we mean only uniform
sequence and consequent certainty. When we declare that children, whose education has been neglected, must fall into evil courses,we declare what experience has shown us will happen in relation to the human mind.
3. Wile!' necessity means neither deductive implication, nor inductive certainty, it refers its to a peculiar test supposed to apply to the truths in dispute—namely, the incon ceivableness of their opposite. It is said that, not only can we not Wicve in the opposite of the axiom, that "the sums of equals are equal," but we cannot even conceire, imagine, i or picture to ourselves the opposite of it. 'Ibis mpossibility of conceiving the contradiction of any statement, is regarded by many as a peculiarly cogent circumstance in its favor. It distinguishes the axiomatic first principles from the truths of inductive science, these having, it is said, an inferior order of certainty. To this it may he replied, how ever, that men's power of conceiving is so much affected by their education and habits, that many things, whose opposites were at one time inconceivable, have since been found to be false. For example, the notion that men could live at the antipodes was once reckoned inconceivable, and we now know it to be a feet. An unvarying association will often produce a disability to conceive anything different.
In commencing a discussion as to the necessary character of any truth, the disputants should agree beforehand which of the three they intend. In the controversy on the mathematical axioms, inninteined between Dringson the one hand, and sir John Herschel and Mr..l. S. Mill on the other, the third meaning is more particularly involved. The doctrine of inconceivability, as the test of truth, has been put forward by Mr. Herbert Spencer, under the title of the universal postulate (Principles cf Pqiciology, Part I).
a river of Texas, rises in the central eastern portion of the state, and flows s. by e., SOO JD., into Sabine bay,where its wuters,with those of the Sabine river, find their way, by Sabine pass, into the gulf of Mexico.