Perhaps it is not unnecessary to repeat, at this point, that events in the brain are not to be regarded as consisting of motions of bits of matter. Matter and motion, as we have seen, are logical constructions using events as their material, and events are therefore something quite different from matter in motion. I take it that, when we have a percept, just what we perceive (if we avoid avoidable sources of error) is an event occupying part of the region which, for physics, is occupied by the brain. In fact, perception gives us the most concrete knowledge we possess as to the stuff of the physical world, but what we perceive is part of the stuff of our brains, not part of the stuff of tables and chairs, sun, moon, and stars. Suppose we are looking at a leaf, and we see a green patch. This patch is not “out there” where the leaf is, but is an event occupying a certain volume in our brains during the time that we see the leaf. Seeing the leaf consists of the existence, in the region occupied by our brain, of a green patch causally connected with the leaf, or rather with a series of events emanating from the place in physical space where physics places the leaf. The percept is one of this series of events, differing from the others in its effects owing to the peculiarities of the region in which it occurs--or perhaps it would be more correct to say that the different effects _are_ the peculiarities of the region. Thus “mind” and “mental” are merely approximate concepts, giving a convenient shorthand for certain approximate laws. In a completed science, the word “mind” and the word “matter” would both disappear, and would be replaced by causal laws concerning “events”, the only events known to us otherwise than in their mathematical and causal properties being percepts, which are events situated in the same region as a brain and having effects of a peculiar sort called “knowledge-reactions”. It will be seen that the view which I am advocating is neither materialism nor mentalism, but what we call “neutral monism”. It is monism in the sense that it regards the world as composed of only one _kind_ of stuff, namely events; but it is pluralism in the sense that it admits the existence of a great multiplicity of events, each minimal event being a logically self-subsistent entity.