Logical Form

Abstract

The term ‘logical form’ is rather a new item in the vocabulary of philosophy and theory of language, though the concept it refers to and the problem involving it seem to be as old as philosophy itself; the first significant contribution to the solution of this problem is due to Aristotle. The problem can be formulated as the following general question: how to describe and to explain the relation of entailment holding between sentences of a language. The description in question is supposed to be empirically adequate in the sense that whenever it implies that a sentence a of a language L follows from a set X of sentences of L then every speaker of L who accepts all sentences belonging to X is apt to accept a as well, within natural limits of human memory and intelligence. The reverse implication is not supposed to be generally true, as the theory is to describe only the phenomenon of acceptance of sentences in virtue of some other sentences and is not expected to cover all cases of simultaneous acceptance of sentences. Some sets of sentences are such that the individual sentences in them are all accepted independently of each other, being generally known as true, e.g. “Snow is white” and “People are mortal”. The precise formulation of the above distinction is rather difficult: it raises the question of empirical evidence with respect to what constitutes the basis of the acceptance of a given sentence by a given person. A partial criterion can be found in the way of justifying the acceptance of a sentence, i.e. in the kind of reasons a person refers to when asked “Why do you believe that ... ?” On the other hand, even if there were empirical evidence that every speaker of a given language is apt to accept a certain sentence on the sole basis of some other sentences, reasons could still exist for excluding this fact from the domain of phenomena explained by the theory in question. This is the case if no structural connections between these sentences can be regarded as indicators of entailment, i.e. if none of them is accompanied by analogous connections of acceptance in all other cases. For this reason no kind of induction nor any superstitious inference is taken into account. The theory one is looking for is supposed to describe and to explain all facts of acceptance of some sentences by virtue of purely structural relations holding between these sentences and some other sentences accepted earlier.