The Oxford Companion to Philosophy Part 54. The book is alphabetized by the whole headings of entries, as distinct from the first word of a heading. Hence, for example, abandonment comes before a priori and a posteriori. It is wise to look elsewhere if something seems to be missing. At the end of the book there is also a useful appendix on Logical Symbols as well as the appendices A Chronological Table of Philosophy and Maps of Philosophy. | 510 Leibniz Gottfried Wilhelm the clarity of the relevant perceptions of the apparent causal agent accompanied by a corresponding decrease in the clarity of the relevant perceptions of the entity apparently acted upon. Leibniz s mature metaphysics includes a threefold classification of entities that must be accorded some degree of reality ideal entities well-founded phenomena and actual existents . monads with their perceptions and appetites. Material objects are examples of well-founded phenomena according to Leibniz while space and time are ideal entities. In the following passage from another letter to de Volder Leibniz formulated the distinction between actual and ideal entities in actual entities there is nothing but discrete quantity namely the multitude of monads . simple substances . . . But continuous quantity is something ideal which pertains to possibles and to actuals insofar as they are possible. Indeed a continuum involves indeterminate parts whereas by contrast there is nothing indefinite in actual entities in which every division that can be made is made. Actual things are composed in the manner that a number is composed of unities ideal things are composed in the manner that a number is composed of fractions. The parts are actual in the real whole but not in the ideal. By confusing ideal things with real substances when we seek actual parts in the order of possibles and indeterminate parts in the aggregate of actual things we entangle ourselves in the labyrinth of the continuum and in inexplicable contradictions. Leibniz s consideration of the labyrinth of the continuum was one source ofhis monadology. Ultimately he reached the conclusion that whatever can be infinitely divided without reaching entities that can not be further divided is not a basic individual in an acceptable ontology. In part Leibniz s reasoning here turns on his beliefs that divisible entities of the sort noted can not satisfy the standards for substantial unity required .
