It does indeed seem hard to find in such a system a place for minds, if one conceives of minds as does the interactionist.  We have seen (section 36) that the interactionist makes the mind act upon matter very much as one particle of matter is supposed to act upon another.  Between the physical and the mental he assumes that there are causal relations; i.e. physical changes must be referred to mental causes sometimes, and mental changes to physical.  This means that he finds a place for mental facts by inserting them as links in the one chain of causes and effects with physical facts.  If he is not allowed to break the chain and insert them, he does not know what to do with them.

The parallelist has not the same difficulty to face.  He who holds that mental phenomena must not be built into the one series of causes and effects with physical phenomena may freely admit that physical phenomena form a closed series, an orderly system of their own, and he may yet find a place in the world for minds.  He refuses to regard them as a part of the world-mechanism, but he relates them to physical things, conceiving them as parallel to the physical in the sense described (sections 37-39).  He insists that, even if we hold that there are gaps in the physical order of causes and effects, we cannot conceive these gaps to be filled by mental phenomena, simply because they are mental phenomena.  They belong to an order of their own.  Hence, the assumption that the physical series is unbroken does not seem to him to crowd mental phenomena out of their place in the world at all.  They must, in any case, occupy the place that is appropriate to them (section 38).

It will be noticed that this doctrine that the chain of physical causes and effects is nowhere broken, and that mental phenomena are related to it as the parallelist conceives them to be, makes the world-system a very orderly one.  Every phenomenon has its place in it, and can be accounted for, whether it be physical or mental.  To some, the thought that the world is such an orderly thing is in the highest degree repugnant.  They object that, in such a world, there is no room for free-will; and they object, further, that there is no room for the activity of minds.  Both of these objections I shall consider in this chapter.

But first, I must say a few words about a type of doctrine lately insisted upon,[1] which bears some resemblance to interactionism as we usually meet with it, and, nevertheless, tries to hold on to the doctrine of the conservation of energy.  It is this:—­

The concept of energy is stretched in such a way as to make it cover mental phenomena as well as physical.  It is claimed that mental phenomena and physical phenomena are alike “manifestations of energy,” and that the coming into being of a consciousness is a mere “transformation,” a something to be accounted for by the disappearance from the physical world of a certain equivalent—­perhaps of some motion.  It will be noticed that this is one rather subtle way of obliterating the distinction between mental phenomena and physical.  In so far it resembles the interactionist’s doctrine.