Of the distinction of natural and moral Necessity, and Inability.
That Necessity which has been explained, consisting in an infallible connexion of the things signified by the subject and predicate of a proposition, as intelligent beings are the subjects of it, is distinguished into moral and natural Necessity.
I shall not now stand to inquire whether this distinction be a proper and perfect distinction; but shall only explain how these two sorts of Necessity are understood, as the terms are sometimes used, and as they are used in the following discourse.
The phrase, moral Necessity, is used variously: sometimes it is used for a Necessity of moral obligation. So we say, a man is under Necessity, when he is under bonds of duty and conscience, from which he cannot be discharged. Again, the word Necessity is often used for great obligation in point of interest. Sometimes by moral Necessity is meant that apparent connexion of things, which is the ground of moral evidence; and so is distinguished from absolute Necessity, or that sure connexion of things, that is a foundation for infallible certainty. In this sense, moral Necessity signifies much the same as that high degree of probability, which is ordinarily sufficient to satisfy mankind, in their conduct and behavior in the world, as they would consult their own safety and interest, and treat others properly as members of society. And sometimes by moral Necessity is meant that Necessity of connexion and consequence, which arises from such moral causes, as the strength of inclination, or motives, and the connexion which there is in many cases between these and such certain volitions and actions. And it is in this sense, that I use the phrase, moral necessity, in the following discourse.
By natural Necessity, as applied to men, I mean such Necessity as men are under through the force of natural causes; as distinguished from what are called moral causes, such as habits and dispositions of the heart, and moral motives and inducements. Thus men, placed in certain circumstances, are the subjects of particular sensations by Necessity: they feel pain when their bodies are wounded; they see the objects presented before them in a clear light, when their eyes are opened: so they assent to the truth of certain propositions, as soon as the terms are understood; as that two and two make four, that black is not white, that two parallel lines can never cross one another; so by a natural Necessity men’s bodies move downwards, when there is nothing to support them.
But here several things may be noted concerning these two kinds of Necessity.
1. Moral Necessity may be as absolute as natural Necessity. That is, the effect may be as perfectly connected with its moral cause, as a natural, necessary effect is with its natural cause. Whether the Will in every case is necessarily determined by the strongest motive, or whether the Will ever makes any resistance to such a motive, or can ever oppose the strongest present inclination, or not; if that matter should be controverted, yet I suppose none will deny, but that, in some cases, a previous bias and inclination, or the motive presented, may be so powerful, that the act of the will may be certainly and indissolubly connected therewith. When motives or previous bias are very strong, all will allow that there is some difficulty in going against them. And if they were yet stronger, the difficulty would be still greater. And therefore, if more were still added to their strength, to a certain degree, it would make the difficulty so great, that it would be wholly impossible to surmount it; for this plain reason, because whatever power men may be supposed to have to surmount difficulties, yet that power is not infinite; and so goes not beyond certain limits. If a man can surmount ten degrees of difficulty of this kind with twenty degrees of strength, because the degrees of strength are beyond the degrees of difficulty; yet if the difficulty be increased to thirty, or an hundred, or a thousand degrees, and his strength not also increased, his strength will be wholly insufficient to surmount the difficulty. As therefore it must be allowed, that there may be such a thing as a sure and perfect connexion between moral causes and effects; so this only is what I call by the name of moral Necessity.
2. When I use this distinction of moral and natural Necessity, I would not he understood to suppose, that if any thing come to pass by the former kind of Necessity, the nature of things is not concerned in it, as well as in the latter. I do not mean to determine, that when a moral habit or motive is so strong, that the act of the Will infallibly follows, this is not owing to the nature of things. But natural and moral are the terms by which thee two kinds of Necessity have usually been called; and they must be distinguished by some names, for there is a difference between them, that is very important in its consequences. This difference, however, does not lie so much in the nature of the connexion, as in the two terms connected. The cause with which the effect is connected, is of a particular kind; viz. that which is of a moral nature; either some previous habitual disposition, or some motive exhibited to the understanding. And the effect is also of a particular kind; being likewise of a moral nature; consisting in some inclination or volition of the soul, or voluntary action.