The truth of the doctrine of necessity will be still more evident if we consider the absurdity of the opposite hypothesis. One of its principal ingredients is self-determination. Liberty, in an imperfect and popular sense, is ascribed to the motions of the animal system, when they result from the foresight and deliberation of the intellect, and not from external compulsion. It is in this sense that the word is commonly used in moral and political reasoning. Philosophical reasoners therefore who have desired to vindicate the property of freedom, not only to our external motions, but to the acts of the mind, have been obliged to repeat this process.
Our external actions are then said to be free when they truly result from the determination of the mind. If our volitions, or internal acts, be also free, they must in like manner result from the determination of the mind, or in other words, "the mind in adopting them" must be "self-determined."
Now nothing can be more evident than that in which the mind exercises its freedom must be an act of the mind. Liberty therefore, according to this hypothesis, consists in this, that every choice we make has been chosen by us, and every act of the mind been preceded and produced by an act of the mind. This is so true that, in reality, the ultimate act is not styled free from any quality of its own, but because the mind, in adopting it, was self-determined, that is, because it was preceded by another act. The ultimate act resulted completely from the determination that was its precursor.