A system of logic for bicategorial ontology

Abstract

In Chapter I of his Some Main Problems of Philosophy G. E. Moore tells us that the first and most important problem of philosophy is to give a general description of the whole Universe.' Now, a general description of reality should, according to Moore, provide the answer to the following fundamental question: what kinds of things are there? There is little doubt that Moore did not use the notion of thing as co-extensive with the notion of material object. Thus, he would probably agree that for all a, if a is anything at all then a is a thing, but he would most certainly deny that for all a, if a is anything at all then a is a material object. But if he used the notion of thing as a sort of most general designation then what did he mean by kinds of things? Is his fundamental question synonymous with the one that asks: what sub-classes of things are there? And if not, in what sense does the latter question differ from the former? In particular, one would like to know how to distinguish between two assertions: the one which says that for some a, and for some b, a's and b's are two different sub-classes of one kind of things, and the one which maintains that for some a, and for some b, a's and b's are two different kinds of things. As regards this problem, we do not get a great deal of help from Moore. Sure enough he discusses a number of answers given to his fundamental question by various philosophers, and from his discussion one could compile a list of what he would be prepared to regard as different kinds of things, but it would be very difficult, if at all possible, to extrapolate from the list general criteria adopted by Moore in his attempts at categorizing reality. However, it would seem to be appropriate to make it clear at this stage that the problem to be dealt with in the present paper is not in fact ontological. I shall not be concerned with propounding arguments either for or against a unicategorial ontology, according to which there is only one kind of things, or a bicategorial ontology, which holds that there are two kinds of things, either kind enjoying a different mode of existence, or any other multicategorial ontology. And although in the end my own