Natural ability is identical with freedom or liberty of will.

It has been, I trust, abundantly shown in a former lecture, and is admitted and insisted on by Edwards:

1. That moral obligation respects strictly only acts of will.

2. That the whole of moral obligation resolves itself into an obligation to be disinterestedly benevolent, that is, to will the highest good of being for its own sake.

3. That willing is the doing required by the true spirit of the moral law. Ability, therefore, to will in accordance with the moral law, must be natural ability to obey God. But:

4. This is and must be the only proper freedom of the will, so far as morals and religion, or so far as moral law is concerned. That must constitute true liberty of will that consists in the ability or power to will, either in accordance with, or in opposition to the requirements of moral law. Or in other words, true freedom or liberty of will must consist in the power or ability to will in every instance either in accordance with, or in opposition to, moral obligation. Observe, moral obligation respects acts of will. What freedom or liberty of will can there be in relation to moral obligation unless the will or the agent has power or ability to act in conformity with moral obligation? To talk of a man's being free to will, or having liberty to will, when he has not the power or ability, is to talk nonsense. Edwards himself holds that ability to do, is indispensable to liberty to do. But if ability to do be a sine qua non of liberty to do, must not the same be true of willing? That is, must not ability to will be essential to liberty to will? Natural ability and natural liberty to will, must then be identical. Let this be distinctly remembered, since many have scouted the doctrine of natural ability to obey God, who have nevertheless been great sticklers for the freedom of the will. In this they are greatly inconsistent. This ability is called a natural ability, because it belongs to man as a moral agent, in such a sense that without it he could not be a proper subject of command, of reward or punishment. That is, without this liberty or ability he could not be a moral agent, and a proper subject of moral government. He must then either possess this power in himself as essential to his own nature, or must possess power, or be able to avail himself of power to will in every instance in accordance with moral obligation. Whatever he can do, he can do only by willing; he must therefore either possess the power in himself directly to will as God commands, or he must be able by willing it to avail himself of power, and to make himself willing. If he has power by nature to will directly as God requires, or by willing to avail himself of power so to will, he is naturally free and able to obey the commandments of God. Then let it be borne distinctly in mind, that natural ability, about which so much has been said, is nothing more nor less than the freedom or liberty of the will of a moral agent. No man knows what he says or whereof he affirms, who holds to the one and denies the other, for they are truly and properly identical.

The human will is free, therefore men have power or ability to do all their duty.

1. The moral government of God everywhere assumes and implies the liberty of the human will, and the natural ability of men to obey God. Every command, every threatening, every argument and denunciation in the Bible implies and assumes this. Nor does the Bible do violence to the human intelligence in this assumption; for:

2. The human mind necessarily assumes the freedom of the human will as a first truth. First truths, let it be remembered, are those that are necessarily assumed by every moral agent. They are assumed always and necessarily by a law of the intelligence, although they may seldom be the direct objects of thought or attention. It is a universal law of the intelligence, to assume the truths of causality, the existence and the infinity of space, the existence and infinity of duration, and many other truths. These assumptions every moral agent always and necessarily takes with him, whether these things are matters of attention or not. And even should he deny any one or all of these first truths, he knows them to be true nevertheless, and cannot but assume their truth in all his practical judgments. Thus, should any one deny the law and the doctrine of causality, as some in theory have done, he knows, and cannot but know, he assumes, and cannot but assume, its truth at every moment. Without this assumption he could not so much as intend, or think of doing, or of any one else doing anything whatever. But a great part of his time, he may not, and does not, make this law a distinct object of thought or attention. Nor is he directly conscious of the assumption that there is such a law. He acts always upon the assumption, and a great part of his time is insensible of it. His whole activity is only the exercise of his own causality, and a practical acknowledgment of the truth, which in theory he may deny. Now just so it is with the freedom of the will, and with natural ability. Did we not assume our own liberty and ability, we should never think of attempting to do anything. We should not so much as think of moral obligation, either as it respects ourselves or others, unless we assumed the liberty of the human will. In all our judgments respecting our own moral character and that of others, we always and necessarily assume the liberty of the human will, or natural ability to obey God. Although we may not be distinctly conscious of this assumption, though we may seldom make the liberty of the human will the subject of direct thought or attention, and even though we may deny its reality, and strenuously endeavor to maintain the opposite, we, nevertheless, in this very denial and endeavor, assume that we are free. This truth never was, and never can be rejected in our practical judgments. All men assume it. All men must assume it. Whenever they choose in one direction, they always assume, whether conscious of the assumption or not, and cannot but assume, that they have power to will in the opposite direction. Did they not assume this, such a thing as election between two ways or objects would not be, and could not be, so much as thought of. The very ideas of right and wrong, of the praiseworthiness, and blameworthiness of human beings, imply the assumption, on the part of those who have these ideas, of the universal freedom of the human will, or of the natural ability of men as moral agents to obey God. Were not this assumption in the mind, it were impossible from its own nature and laws that it should affirm moral obligation, right or wrong, praiseworthiness or blameworthiness of men. I know that philosophers and theologians have in theory denied the doctrine of natural ability or liberty, in the sense in which I have defined it; and I know, too, that with all their theorizing, they did assume, in common with all other men, that man is free in the sense that he has liberty or power to will as God commands. I know that, but for this assumption, the human mind could no more predicate praiseworthiness or blameworthiness, right or wrong of man, than it could of the motions of a windmill. Men have often made the assumption in question without being aware of it, have affirmed right and wrong of human willing without seeing and understanding the conditions of this affirmation. But the fact is, that in all cases the assumption has lain deep in the mind as a first truth, that men are free in the sense of being naturally able to obey God: and this assumption is a necessary condition of the affirmation that moral character belongs to man.

What constitutes moral inability, according to Edwards and those who hold with him.