LOGICAL POSSIBILITY AND NECESSARY TRUTH: THE VIEWPOINT FROM AN INTENTIONAL LOGIC

DOUGLAS BRUCE RASMUSSEN, Marquette University

Abstract

This essay seeks to show that there can be necessary truths with ontological or factual import. Yet, since at least Hume the question of whether necessary truths can be ontological or factual has generally been answered negatively by empiricists. One of the central reasons for denying necessary truths ontological or factual import has been an argument that this essay has labeled the 'logical possibility argument'. According to this argument no proposition can be considered a necessary truth if its denial is logically possible, and any proposition whose denial is conceivable or imaginable has a denial which is logically possible. This argument claims, for example, that it is logically possible for a solid iron bar to float when placed in water or a cat to give birth to pups, for these putative events are conceivable or imaginable. Thus, the propositions "Solid iron bars sink when placed in water" and "Cats cannot give birth to pups" constitute merely contingent truths--truths which could be otherwise. Furthermore, the logical possibility argument is usually taken as showing that no proposition about beings in rerum natura can be a necessary truth. It is claimed that the contrary of any matter of fact is always conceivable and therefore always logically possible. This essay argues that the logical possibility argument is highly dubious and should not be used as a basis for determining whether a proposition is a necessary truth. The reasons for this are very complex, but they involve rejecting the use of the procedure of inspectio mentis to determine what is conceivable, the equation of imagining with conceiving, and the equivocal use of the phrase 'it is logically possible that'. The result of which is that there is a sense in which solid iron bars and cats cannot respectively be conceived as floating on water or giving birth to pups, and this sense of 'conceive' is appropriate to the logical possibility argument. This insight allows for a defense of H. W. B. Joseph's justification of the principle of the uniformity of nature against criticisms advanced by A. J. Ayer and the claim that science can yield necessary truths. Overall, the rejection of the logical possibility argument and defense of the claim that necessary truths can be ontological or factual involves arguing: (1) that purely formal/linguistic theories of necessary truth fail to provide an explanation of necessary truth; (2) that the analytic/synthetic characterization of propositions badly misconstrues the nature of a proposition; (3) that Quine's criticism of essentialism and the possibility of scientific realism fails; and most importantly (4) that logic should be considered as "intentional" in nature and not as a purely formal or metaphysical enterprise. These four points, as well as the specific reasons for rejecting the logical possibility argument, are developed in this essay. In many respects this essay can be construed as an attempt to defend and develop a view of necessary truth and logic that belongs to an Aristotelian metaphysical and epistemological tradition, a view which for the most part has been ignored by contemporary philosophy.

Recommended Citation

RASMUSSEN, DOUGLAS BRUCE, "LOGICAL POSSIBILITY AND NECESSARY TRUTH: THE VIEWPOINT FROM AN INTENTIONAL LOGIC" (1980). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI8111864.
https://epublications.marquette.edu/dissertations/AAI8111864

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