frequently repeating them; so it is that all our knowledge is accumulated; and so it is that all our thinking is conducted. A wholly new field of inquiry is thus opened up. By using our own consciousness as a physiological instrument of the greatest delicacy, we are able to learn a great deal about the dynamics of brain-action concerning which we should otherwise remain in total ignorance. But the field of inquiry thus opened up is too large for me to enter upon to-day. I will therefore merely observe, in general terms, that although we are still very far from understanding the operations of the brain in thought, there can be no longer any question that in these operations of the brain we have what I may term the objective machinery of thought. 'Not every thought to every thought succeeds indifferently,' said Hobbes. Starting from this fact, modern physiology has clearly shown why it is a fact; and looking to the astonishing rate at which the science of physiology is now advancing, I think we may fairly expect that within a time less remote than the two centuries which now separate us from Hobbes, the course of ideas in a given train of thought will admit of having its footsteps tracked in the corresponding pathways of the brain. Be this, however, as it may, even now we know enough to say that, whether or not these footsteps will ever admit of being thus tracked in detail, they are all certainly present in the cerebral structures of each one of us. What we know on the side of mind as logical sequence, is on the side of the nervous system nothing more than a passage of nervous energy through one series of cells and fibres rather than through another: what we recognize as truth is merely the fact of the brain vibrating in tune with Nature. * * * * *