Logic and Reality in Leibniz's Metaphysics (review)

BOOK REVIEWS 297 derived (or should have derived) from his logic, and to attempt to evaluate that logic and the metaphysics which is ostensibly derived from it. In general, Parkinson is concerned with indicating that Bertrand Russell's contention that Leibniz's metaphysics is directly derived from his logic is, to some extent, correct, but is ultimately incorrect. Specifically, he argues that Leibniz did, indeed, derive some of his metaphysical assertions from his logic; but, in addition, he appealed to basic theistic beliefs in order to support his metaphysical conclusions. In discussing the general nature of Leibniz's logic, Parkinson points out that Leibniz tends to regard the proposition from the intensional rather than from the extensional viewpoint, that true propositions are those in which the concept of the predicate is "contained in" the concept of the subject, and that relational propositions can be reduced to subject-predicate form. In regard to this last point, it is said that Leibniz has no defense against Russell's critique of this assumption (that relational propositions can be reduced to subject-predicate propositions) since it is clearly not the case in asymmetrical relationships. In addition, Parldnson argues that hypothetical propositions asserting a causal relationship cannot be treated like other hypothetical propositions (i.e., those propositions which can be reduced to propositions in which the inclusion of the concept of the predicate in the subject is asserted), since the denial of the truth of such a proposition does not involve contradiction. Another basic difficulty in Leibniz's conception of logic is that he is unable to account for existential propositions. Precisely because of the limitations of Leibniz's conception of the structure of the proposition, it is said, it is not obvious that his logic is directly related to a specific metaphysics insofar as this logic does not entail certain propositions which assert what the "world" must be like. In effect, Leibniz's metaphysics is not derived from his conception of the structure of propositions. The single most significant principle of Leibniz's thought is the principle of sufficient reason. Generally speaking, this principle can be formulated as follows: There must be a sufficient reason for anything that is or happens. This formulation is also expressed as the view that nothing happens without a cause. It is clear that Leibniz tends to use the words "reason" and "cause" interchangeably. This leads him, as Schopenhauer pointed out in his essay on the Four]old Root o] Causation (though he refers specifically to Spinoza's similar usage), to speak at one and the same time on a logical and an ontological level. Leibniz himself, as Parkinson points out, began to make this distinction because he saw that God cannot be said to have a "cause" for his existence, but it is possible to give a reason for the existence of what is eternal (p. 66). Nevertheless, the principle of sufficient reason, as applied to Leibniz's conception of truth, means that no true proposition , the "reason" of which could not be "seen" by an individual who had sufficient knowledge to understand it perfectly or could provide an a pr/or/ proof of its truth, would be such. Although a necessary truth is one which could be shown to be true by virtue of an a pr/or/ proof, we cannot demonstrate the truth of a contingent truth. A truth is contingent if its truth is known by non-deductive means. Thus, although contingent truths have reference to a phenomenon or event which has a "reason" for its having occurred, it is impossible to demonstrate the truth of this statement since such a demonstration would involve an infinite number of operations. The complete analysis of the "concept" in contingent truth is possible only for a divine being. The implications of this view are (a) that, for God, there are no contingent truths, but only necessary truths; (b) that finite beings (men) come to know the truth of contingent statements through sense perception (an imperfect mode of cognition). What Leibniz fails to do (although Parkinson does not deal with this question) is to follow through the implications of this view; that is, he did not say that there...