These all properly come under the denomination of _natural_, because they are alike _necessitated_. "Whatever is comprised in the chain and mechanism of cause and effect, of course necessitated, and having its necessity in some other thing antecedent or concurrent,--this is said to be _natural_; and the aggregate and system of all such things is _nature_." Now spirit, as a cause or agent, by this system, comes under the same definition: in all its acts it is necessitated. It is in will particularly that man is taken as a cause or agent, because it is by will that he directly produces phenomena or effects; and by this system it is not possible to distinguish, so far as necessary connexion is considered, a chain of antecedents and sequents made up of motives, volitions, and the consequents of volitions, from a chain of sequents and antecedents into which the three first mentioned classes of natural agents enter. All the several classes have peculiar and distinguishing characteristics; but in the relation of antecedence and sequence,--their relation as causes or agents producing effects,--no distinction can be perceived. Wind, water, &c. form one kind of cause; organic life forms another; brute organization and sensitivity another; intelligent volition another: but they are all necessary, absolutely necessary; and therefore they are the co-ordinate parts of the one system of nature. The difference which exists between them is a difference of terms merely. There is no difference in the nature of the relation between the terms. The nature of the relation between the water-wheel and the water,--of the relation between the organic life of plants and their developement,--of the relation between passion and volition in brutes,--of the relation between their efforts and material effects,--and the nature of the relation between motive and volition,--are one: it is the relation of cause and effect considered as stated antecedent and sequent, and no more and no less necessary in one subject than in another. XII. It follows, again, that sensations produced by external objects, and all emotions following perception, and all the acts of the intelligence, whether in intuitive knowledge or in ratiocination, are as really our acts, and acts for which we are as really responsible, if responsibility be granted to exist, as acts of volition. Sensations, emotions, perceptions, reasonings, are all within us; they all lie in our consciousness; they are not created by our volitions, like the motions of the hands and feet; they take place by their own causes, just as volitions take place by their causes. The relation of the man to all is precisely the same. He is in no sense the cause of any of these affections of his being; he is simply the subject: the subject of sensation, of perception, of emotion, of reasoning, and of volition; and he is the subject of all by the same necessity.