namely, that conscious intellectual existence is _necessarily_ associated with that form of existence which we know phenomenally as Matter and Motion. If it is true that a "a moving molecule of inorganic matter does not possess mind or consciousness, but it possesses a small piece of Mind-stuff," then assuredly the central position of Materialism is shown to be impregnable. For while it remains as true as ever that mind and consciousness can only emerge when what we know phenomenally as "Matter takes the complex form of a living brain," we have abolished the necessity for assuming even a causal connection between the substance of what we know phenomenally as Matter and the substance of what we know phenomenally as Mind: we have found that, in the last resort, the phenomenal connection between what we know as Matter and what we know as Mind is actually even more intimate than a connection of causality; we have found that it is a substantial identity. To sum up this discussion. We have considered the bearing of modern speculation on the doctrine of Materialism in three successive stages of argument. First, we had to consider the bearing on Materialism of the simple doctrine of Relativity. Here we saw that Materialism was only affected to the extent of being compelled to allow that what we know as Matter and Motion are not known as they are in themselves. But we also saw that, as the inscrutable realities are uniformly translated into consciousness as Matter and Motion, it still remains as true as ever that _what we know_ as Matter and Motion may be the causes of what we know as Mind. Even, therefore, if the supposition of causality is taken to be an essential feature of Materialism, Materialism would be in no wise affected by substituting for the words Matter and Motion the symbols _x_ and _y_. The second of the three stages consisted in showing that Mr. Spencer's argument as to the possible identity of Force and Feeling is not in itself sufficient to overthrow the doctrine that what we know as Matter and Motion may be the cause of what we know as Mind. For the mere fact of its being more _conceivable_ that units of Force should resemble units of Feeling than conversely, is no warrant for concluding that in reality any corresponding probability obtains. The test of conceivability, although the most ultimate test that is available, is here rendered vague and valueless by the _a priori_ consideration that _whatever_ the cause of Mind may be (if it has a cause), we must find it more easy to conceive of this cause as resembling Mind than to conceive of it as resembling any other entity of which we are only conscious indirectly.