The advocates of necessity contend, not only that volition is the effect of motive, but also that “to be an effect implies _passiveness_, or the being subject to the power and action of its cause.”(125) Such precisely is the doctrine of Edwards, and Collins, and Hobbes. In this sense of the word it is denied that motive is the cause of volition, and it is affirmed that mind is the cause thereof. Thus, says Dr. Samuel Clarke, in his reply to Collins, “’Tis the self-moving principle, and not at all the reason or motive, which is the _physical_ or _efficient_ cause of action;” by which we understand him to mean volition, as that is the thing in dispute. Now, when the advocates of free-agency insist that motive is not the efficient cause of volition, and that mind is the efficient cause thereof, we suppose them to employ the expression, _efficient cause_, in one and the same sense in both branches of the proposition. This is the only fair way of viewing their language; and if they wished to be understood in any other manner, they should have taken the pains to explain themselves, and not permit us to be misled by an ambiguity. Here the precise point in dispute is clearly presented; and let us hear the contending parties, before we proceed to decide between them. You are in error, says the necessitarian to his opponents, in denying that motive, and in affirming that mind, is the efficient cause of volition. For if an act of the mind, or a volition, is caused by the mind, it must be produced by a preceding act of the mind, and this act must be produced by another preceding act of the mind, and so on _ad infinitum_; which reduces the matter to a plain impossibility. Now, if the necessitarian has not been deceived by an unwarrantable ambiguity on the part of his adversary, he has clearly reduced his doctrine to the absurdity of an infinite series of acts: that is to say, if the advocate of free-agency does not depart from the ordinary meaning of words, when he affirms that mind is the _efficient cause_ of volition; and if he does not use these terms “_efficient cause_,” in different senses in the same sentence, then we feel bound to say that he is fairly caught in the toils of his adversary. But we are not yet in condition to pass a final judgment between the parties. The necessitarian contends that “volition, or an act of the mind, is the effect of motive, and that it is subject to the power and action of its cause.”(126) The advocate of free-will replies, If we must suppose an action of motive on the mind to account for its act, we must likewise suppose another action to account for the action of motive; and so on _ad infinitum_. Thus the necessitarian seems to be fairly caught in his own toils, and entrapped by his own definition and arguments.