Nor does the exercise of this right, charge him with mutability; for, if the conduct of God invariably tends to promote human happiness, consistently with the freedom of man, his immutability must remain entire, while that end is kept in view. The mutability of man renders a change of means in God absolutely necessary, in order to preserve the stability of his original purposes: for a uniform application of the same measures, through all the vicissitudes of human instability, instead of uniformly tending towards human happiness, must tend, in many instances, to the completion of human misery: and, in this case, God might be justly charged with mutability, in deserting those purposes and designs which he once promoted. But, in all the apparent variations which we discover, in the moral, as well as the natural world, he is no more chargeable with mutability, than the mariner, who alters his course and shifts his sails, through the progress of his voyage, to arrive at the port of his destination.

These things being premised, the question is, whether God can so far accept a vicarious sacrifice, in the person of the innocent, as to permit his mercy to interfere in the behalf of the guilty. The question is not, in the present case, whether moral justice can accept the innocent for the guilty; but, whether God by receiving, in suffering, an equivalent for the offence committed, can, on a principle of mercy, discharge the guilty; and do this, as it relates to himself, consistently with the rectitude and justice of his nature.

As salvation is uniformly ascribed, in the Bible, to mercy, the question simply is, whether God can possibly show mercy, without being unjust. In the nature of things, justice cannot show mercy; for if any act be of justice, it is no longer of mercy;  nevertheless, mercy, when exercised, must be so consistent with justice, that it cannot be unjust. Now, admitting the existence of moral evil in man, and the existence of moral justice in God, it follows, that these cannot meet together, without destroying human happiness; because the two principles are incompatible with each other. To destroy this incompatibility, either moral evil or moral justice must cease. It cannot be moral justice; therefore, it must be moral evil. But, admitting that moral evil could be extracted from the human mind without any expiation, still, the turpitude of those actions, which resulted from the evil principle, while it predominated, being a positive insult offered to moral justice, necessarily requires an expiation, in order to its annihilation. This expiation must, in order to be available, be abstracted from all evil; but, all mankind being infected by evil, no one, among the human race was adequate to the task. It must then follow, that some other substitute must be found; and we find every necessary qualification concentrated in the person of Jesus Christ.

That moral justice is obligatory on man, must be admitted; and then it must follow, that every deviation from that principle, subjects to punishment; this is evident, from our standing in need of mercy; and, if justice has an additional claim upon every offender, it must also follow, that his claim cannot be relinquished without an expiation: to suppose otherwise, is to reduce justice to an indiscriminate caprice. This claim must be cancelled, either by man or God. If by man, it destroys every idea of future happiness; if by God, it must be, by accepting the innocent for the guilty. But, as the hope of future happiness is not destroyed, the claim must be cancelled by God: and, consequently, it must be by his accepting the innocent instead of the guilty.

Nor can justice accept of an offering made by one guilty person in the behalf of another; for, wherever guilt is found, it entitles its possessor to punishment; and punishment cannot have any thing in it meritorious. Nothing but merit can be available for the guilty; and, therefore, guilt must be expiated by innocence; which innocence must be so far accepted by commutative justice, as to permit mercy to operate in the behalf of the guilty. Finally, if we allow ourselves to be guilty, and God to be just, and yet hope for happiness from him, it must be admitted, that he can accept the innocent in the room of the guilty; and, that he does, in mercy, discharge them, and render them capable of happiness, through the efficacy of suffering innocence. And, if we grant mercy to exist with God, it must be, to entitle those who are the objects of it, to those favours, to which, through justice, they can have no claim.