This brings us to freedom of thought. This lies in the fact, not merely that we can think, but that we can and desire to think rightly, and that we are able to measure our thoughts by the standard of “true” or “false.” Naturalism is proud of the fact that it desires nothing more than to search after truth. To this it is ready to sacrifice all expressions of feeling or sentiment, and all prejudices. The truth, the whole truth, and nothing but the truth is its ideal, even if all pet ideas have to give way before it. It usually saddles itself with the idea of the good and the beautiful along with this “idea of truth,” but is resolved, since it must soon see for itself that it is able to secure only a very doubtful basis for these, to sacrifice them to truth if need be. This is worthy of honour,(107) but it implies a curious self-deception. For if naturalism be in the right, thought is not free, and if thought be not free there can be no such thing as truth, for there can be no establishing of what truth is. Let us attempt to make this plain in the following manner: According to the naturalistic-psychological theory, the play of our thoughts, our impressions of things and properties, their combination in judgments or in “perceptions,” are dependent on physiological processes of the brain, and therefore upon natural laws, or, according to some, on peculiar attractions and repulsions among the impressions themselves, regulated by the laws of association. If that and that only were the case, I should be able to say that such a conception was present in my mind, or that this or that thought had arisen in me, and I might perhaps be able to trace the connection which made it necessary that it should arise at that particular time. But every thought would be equally right. Or rather there could be no question of right or wrong in the matter at all. I could not forbid any thought to be there, could not compel it to make way for another, perhaps exactly its opposite. Yet I do this continually. I never merely observe what thoughts are in my own mind or in another’s. For I have a constant ideal, a plumb-line according to which I measure, or can measure, every train of thought. And I can compel others to apply this same plumb-line to their thoughts. This plumb-line is logic. It is the unique law of the mind itself which concerns itself about no law of nature or of association whatsoever. And however mighty a flood of conceptions and associations may at times pour through me in consequence of various confused physiological states of excitement affecting the brain, or in consequence of the fantastic dance of the associations of ideas, the ego is always able in free thought to intervene in its own psychical experiences, and to test which combinations of ideas have been logically thought out and are therefore right, and which are wrong. It often enough refrains from exercising this control, leaving the lower courses of thought free play.