On the above definitions I remark:

1. That they mutually exclude each other. To predicate Liberty of any phenomenon is to affirm that it is not necessary. To predicate Necessity of it, is equivalent to an affirmation that it is not free.

2. They are strictly and absolutely universal in their application. All antecedents and consequents, whatever the nature of the subjects thus connected may be, must fall under one or the other of these relations. As the terms right and wrong, when correctly defined, will express the nature of all moral actions, actual and conceivable, so the terms Liberty and Necessity, as above defined, clearly indicate the nature of the relation between all antecedents and consequents, real and supposable. Take any antecedent and consequent we please, real or conceivable, and we know absolutely, that they must sustain to each other one or the other of these relations. Either in connection with this antecedent, but this one consequent is possible, and this must arise, or in connection with the same antecedent, either this, or one or more different consequents are possible, and consequently equally so: for possibility has, in reality, no degrees.

3. All the phenomena of the Will, sustaining, as they do, the relation of consequents to motives considered as antecedents, must fall under one or the other of these relations. If we say, that the relation between motives and acts of Will is that of certainty, still this certainty must arise from a necessary relation between the antecedent and its consequent, or it must be of such a nature as consists with the relation of Liberty, in the sense of the term Liberty as above defined.

4. The above definitions have this great advantage in our present investigations. They at once free the subject from the obscurity and perplexity in which it is often involved by the definitions of philosophers. They are accustomed, in many instances, to speak of moral necessity and physical necessity, as if these are in reality different kinds of necessity: whereas the terms moral and physical, in such connections, express the nature of the subjects sustaining to each other the relations of antecedents and consequents, and not at all that of the relation existing between them. This is exclusively expressed by the term Necessity—a term which designates a relation which is always one and the same, whatever the nature of the subjects thus related may be. An individual in a treatise on natural science, might, if he should choose, in speaking of the relations of antecedents and consequents among solid, fluid, and aeriform substances, use the words, solid necessity, fluid necessity, and aeriform necessity. He might use as many qualifying terms as there are different subjects sustaining to each other the relation under consideration. In all such instances no error will arise, if these qualifying terms are distinctly understood to designate, not the nature of the relation of antecedent and consequent in any given case (as if there were as many different kinds of necessity as there are qualifying terms used), but to designate the nature of the subjects sustaining this relation. If, on the other hand, the impression should be made, that each of these qualifying terms designates a necessity of a peculiar kind, and if, as a consequence, the belief should be induced, that there are in reality so many different kinds of necessity, errors of the gravest character would arise—errors no more important, however, than actually do arise from the impression often induced, that moral necessity differs in kind from physical necessity.

5. I mention another very decisive advantage which the above definitions have in our present investigations. In the light of the terms Liberty and Necessity, as above defined, the two great schools in philosophy and theology are obliged to join issue directly upon the real question in difference between them, without the possibility on the part of either, of escaping under a fog of definitions about moral necessity, physical necessity, moral certainty, &c., and then claiming a victory over their opponents. These terms, as above defined, stand out with perfect clearness and distinctness to all reflecting minds. Every one must see, that the phenomena of the Will cannot but fall under the one or the other of the relations designated by these terms inasmuch as no third relation differing in kind from both of these, is conceivable. The question therefore may be fairly put to every individual, without the possibility of misapprehension or evasion—Do you believe, whenever a man puts forth an act of Will, that in those circumstances, this one act only is possible, and that this act cannot but arise? In all prohibited acts, for example, do you believe that an individual, by the resistless providence of God, is placed in circumstances in which this one act only is possible, and this cannot but result, that in these identical circumstances, another and a different act is required of him, and that for not putting forth this last act, he is justly held as infinitely guilty in the sight of God, and of the moral universe? To these questions every one must give an affirmative or negative answer. If he gives the former, he holds the doctrine of Necessity, and must take that doctrine with all its consequences. If he gives the latter, he holds the doctrine of Liberty in the sense of the term as above defined. He must hold, that in the identical circumstances in which a given act of Will is put forth, another and different act might have been put forth; and that for this reason, in all prohibited acts, a moral agent is held justly responsible for different and opposite acts. Much is gained to the cause of truth, when, as in the present instance, the different schools are obliged to join issue directly upon the real question in difference between them, and that without the possibility of misapprehension or evasion in respect to the nature of that question.