Metaphysics

In the 20th century the validity of metaphysical thinking was disputed by the logical positivists (see Analytic and Linguistic Philosophy) and by the so-called dialectical materialism of the Marxists. The basic principle maintained by the logical positivists is the verifiability theory of meaning. According to this theory a sentence has factual meaning only if it can in principle be verified by empirical observation. Logical positivists argue that metaphysical expressions such as “nothing exists except material particles” and “everything is part of one all-encompassing spirit” cannot be tested empirically. Therefore, according to the verifiability theory of meaning, these expressions have no factual meaning, although they can have an emotive meaning relevant to human hopes and feelings.

The dialectical materialists assert that the mind is conditioned by and reflects material reality. Therefore, speculations that conceive of constructs of the mind, such as the categories of metaphysics, as having any reality of their own are themselves unreal and can result only in delusion. To these assertions metaphysicians reply by denying the adequacy of the verifiability theory of meaning and of material perception as the standard of reality. Both logical positivism and dialectical materialism, they argue, conceal metaphysical assumptions, for example, that everything is observable or at least connected with something observable and that the mind has no distinctive life of its own. In the philosophical movement known as existentialism, thinkers have contended that the questions of the nature of being and of the individual’s relationship to it are extremely important and meaningful in terms of human life. The investigation of these questions is therefore considered valid whether or not its results can be verified objectively.

Since the 1950s the problems of systematic analytical metaphysics have been studied in Britain by Stuart Newton Hampshire and Peter Frederick Strawson, the former concerned, in the manner of Spinoza, with the relationship between thought and action, and the latter, in the manner of Kant, with describing the major categories of experience as they are embedded in language. In the United States metaphysics has been much pursued in the spirit of positivism by Wilfred Stalker Sellars and Willard Van Orman Quine. Sellars has sought to express metaphysical questions in linguistic terms, and Quine has attempted to determine whether the structure of language commits the philosopher to asserting the existence of any entities whatever and, if so, what kind. In these new formulations the issues of metaphysics and ontology remain vital.