He regards mental phenomena and physical phenomena as links in the one chain of causes and effects. Shall he hold that certain mental links are "free-will" links, that they are wholly unaccountable? If he does, all that has been said above about the "free-willist" applies to him. He believes in a disorderly world, and he should accept the consequences of his doctrine. 47. THE PHYSICAL WORLD AND THE MORAL WORLD.--I have said a little way back that, when we think of bodies as having minds, we are introduced to a world of distinctions which have no place in the realm of the merely physical. One of the objections made to the orderly world of the parallelist was that in it there is no room for the activity of minds. Before we pass judgment on this matter, we should try to get some clear notion of what we may mean by the word "activity." The science of ethics must go by the board, if we cannot think of men as _doing_ anything, as acting rightly or acting wrongly. Let us conceive a billiard ball in motion to come into collision with one at rest. We commonly speak of the first ball as active, and of the second as the passive subject upon which it exercises its activity. Are we justified in thus speaking? In one sense, of course, we are. As I have several times had occasion to remark, we are, in common life, justified in using words rather loosely, provided that it is convenient to do so, and that it does not give rise to misunderstandings. But, in a stricter sense, we are not justified in thus speaking, for in doing so we are carrying over into the sphere of the merely physical a distinction which does not properly belong there, but has its place in another realm. The student of mechanics tells us that the second ball has affected the first quite as much as the first has affected the second. We cannot simply regard the first as cause and the second as effect, nor may we regard the motion of the first as cause and the subsequent motion of the second as its effect alone. _The whole situation at the one instant_--both balls, their relative positions and their motion and rest--must be taken as the cause of _the whole situation at the next instant_, and in this whole situation the condition of the second ball has its place as well as that of the first. If, then, we insist that to have causal efficiency is the same thing as to be active, we should also admit that the second ball was active, and quite as active as the first. It has certainly had as much to do with the total result. But it offends us to speak of it in this way. We prefer to say that the first was active and the second was acted upon. What is the source of this distinction?