There is, however, another question, not quite the same as this, namely the question as to the relations of psychology and physics. If we knew more, would psychology be absorbed in physics? or, conversely, would physics be absorbed in psychology? A man may be a materialist and yet hold that psychology is an independent science; this is the view taken by Dr. Broad in his important book on _The Mind and its Place in Nature_. He holds that a mind is a material structure, but that it has properties which could not, even theoretically, be inferred from those of its material constituents. He points out that structures very often have properties which, in the present state of our knowledge, cannot be inferred from the properties and relations of their parts. Water has many properties which we cannot infer from those of hydrogen and oxygen, even if we suppose ourselves to know the structure of the molecule of water more completely than we do as yet. Properties of a whole which cannot, even theoretically, be inferred from the properties and relations of its parts are called by Dr. Broad “emergent” properties. Thus he holds that a mind (or brain) has properties which are “emergent”, and to this extent psychology will be independent of physics and chemistry. The “emergent” properties of minds will only be discoverable by observation of minds, not by inference from the laws of physics and chemistry. This possibility is an important one, and it will be worth while to consider it. Our decision to regard a unit of matter as itself not ultimate, but an assemblage of events, somewhat alters the form of our question as to “emergent” properties. We have to ask: Is matter emergent from events? Is mind emergent from events? If the former, is mind emergent from matter, or deducible from the properties of matter, or neither? If the latter, is matter emergent from mind or deducible from the properties of mind, or neither? Of course, if neither mind nor matter is emergent from events, these latter questions do not arise. Let us coin a word, “chrono-geography”, for the science which begins with events having space-time relations and does not assume at the outset that certain strings of them can be treated as persistent material units or as minds. Then we have to ask ourselves first: can the science of matter, as it appears in physics and chemistry, be wholly reduced to chrono-geography? If no, matter is emergent from events; if yes, it is not emergent.