The principal theories that have been advocated, so far as my knowledge extends, are the following:

1. The taste scheme.

2. The divine efficiency scheme.

3. The susceptibility scheme.

4. The divine moral suasion scheme.

1. The taste scheme.

This theory is based upon that view of mental philosophy which regards the mental heart as identical with the sensibility. Moral depravity, according to this school, consists in a constitutional relish, taste, or craving for sin. They hold the doctrine of original sin of a sinful nature or constitution, as was shown in my lectures on moral depravity. The heart of the mind, in the estimation of this school, is not identical with choice or intention. They hold that it does not consist in any voluntary state of mind, but that it lies back of, and controls voluntary action, or the actions of the will. The wicked heart, according to them, consists in an appetency or constitutional taste for sin, and with them, the appetites, passions, and inclinations of human nature in its fallen state, are in themselves sinful. They often illustrate their ideas of the sinful taste, craving, or appetite for sin, by reference to the craving of carnivorous animals for flesh.

A change of heart, in the view of this philosophy, must consist in a change of constitution. It must be a physical change, and wrought by a physical, as distinguished from a moral agency. It is a change wrought by the direct and physical power of the Holy Spirit in the constitution of the soul, changing its susceptibilities, implanting or creating a new taste, relish, appetite, craving for, or love of, holiness. It is, as they express it, the implantation of a new principle of holiness. It is described as a creation of a new taste or principle, as an infusion of a holy principle, etc. This scheme, of course, holds and teaches that, in regeneration, the subject is entirely passive. With this school, regeneration is exclusively the work of the Holy Spirit, the subject having no agency in it. It is an operation performed upon him, may be, while he is asleep, or in a fit of derangement, while he is entirely passive, or perhaps when at the moment he is engaged in flagrant rebellion against God. The agency by which this work is wrought, according to them, is sovereign, irresistible, and creative. They hold that there are of course no means of regeneration, as it is a direct act of creation. They hold the distinction already referred to and examined, between regeneration and conversion; that when the Holy Spirit has performed the sovereign operation and implanted the new principle, then the subject is active in conversion, or in turning to God.

They hold that the soul, in its very nature, is enmity against God; that therefore the gospel has no tendency to regenerate or convert the soul to God; but, on the contrary, that previous to regeneration by the sovereign and physical agency of the Holy Spirit, every exhibition of God made in the gospel, tends only to inflame and provoke this constitutional enmity.

They hold, that when the sinful taste, relish, or craving for sin is weakened, for they deny that it is ever wholly destroyed in this life, or while the soul continues connected with the body, and a holy taste, relish, or craving is implanted or infused by the Holy Spirit into the constitution of the soul, then, and not till then, the gospel has a tendency to turn or convert the sinner from the error of his ways.

As I have said, their philosophy of moral depravity is the basis of their philosophy of regeneration. It assumes the dogma of original sin, as taught in the Presbyterian Confession of Faith, and attempts to harmonize the philosophy of regeneration with that philosophy of sin, or moral depravity.

Upon this scheme or theory of regeneration, I remark:

(1.) That it has been sufficiently refuted in the lectures on moral depravity. If, as was then shown, moral depravity is altogether voluntary, and consists in selfishness, or in a voluntary state of mind, this philosophy of regeneration is of course without foundation.

(2.) It was shown in the lectures on moral depravity, that sin is not chosen for its own sake, that there is no constitutional relish, taste, or craving for sin, that in sinful choice, sin is not the end or object chosen, but that self-gratification is chosen, and that this choice is sinful. If this is so, then the whole philosophy of the taste scheme turns out to be utterly baseless.

The taste, relish, or craving, of which this philosophy speaks, is not a taste, relish or craving for sin, but for certain things and objects, the enjoyment of which is, to a certain extent, and upon certain conditions, lawful. But when the will prefers the gratification of taste or appetite to higher interests, this choice or act of will is sin. The sin never lies in the appetite, but in the will's consent to unlawful indulgence.

(3.) This philosophy confounds appetite or temptation to unlawful indulgence, with sin. Nay, it represents sin as consisting mostly, if not altogether, in that which is only temptation.

(4.) It throws the blame of unregeneracy upon God. If the sinner is passive, and has no agency in it; if it consists in what this philosophy teaches, and is accomplished in the manner which this theory represents, it is self-evident that God alone is responsible for the fact, that any sinner is unregenerate.

(5.) It renders holiness after regeneration physically necessary, just as sin was before, and perseverance also as physically necessary, and falling from grace as a natural impossibility. In this case holy exercises and living are only the gratification of a constitutional appetite, implanted in regeneration. Let us consider next: