In the diagram Mr. X has been linked to the cycle at a particular point in deference to his supposed claim that he knows matter; but a little reflection will show that the point of contact of mind with the physical universe is not very definite. Mr. X knows a table; but the point of contact with his mind is not in the material of the table. Light waves are propagated from the table to the eye; chemical changes occur in the retina; propagation of some kind occurs in the optic nerves; atomic changes follow in the brain. Just where the final leap [Pg 268] into consciousness occurs is not clear. We do not know the last stage of the message in the physical world before it became a sensation in consciousness. This makes no difference. The physical entities have a cyclic connection, and whatever intrinsic nature we attribute to one of them runs as a background through the whole cycle. It is not a question whether matter or electricity or potential is the direct stimulus to the mind; in their physical aspects these are equally represented as pointer readings or schedules of pointer readings. According to our discussion of world building they are the measures of structure arising from the comparability of certain aspects of the basal relations—measures which by no means exhaust the significance of those relations. I do not believe that the activity of matter at a certain point of the brain stimulates an activity of mind; my view is that in the activity of matter there is a metrical description of certain aspects of the activity of mind. The activity of the matter is our way of recognising a combination of the measures of structure; the activity of the mind is our insight into the complex of relations whose comparability gives the foundation of those measures.