The Approach to Philosophy

by Ralph Barton Perry

§ [75]. Logic is the formulation, as independently as possible of special subject-matter, of that which conditions truth in belief. Since logic is concerned with truth only in so far as it is predicated of belief, and since belief in so far as true is knowledge, logic can be defined as the formulation of the most general principles of knowledge. The principles so formulated would be those virtually used to justify belief or to disprove the imputation of error.

The Parts of Formal Logic. Definition, Self-evidence, Inference, and Observation.

§ [76]. What is called formal logic is animated with the hope of extracting these formulations directly from an analysis of the procedure of thought. The most general logical principles which have appeared in the historical development of formal logic are definition, self-evidence, inference, and observation. Each of these has been given special study, and each has given rise to special issues.

Definition has to do with the formation of concepts, or determinate and unequivocal meanings. The universality of such concepts, and their consequent relation to particular things, was, as we have seen, investigated at a very early date, and gave rise to the great realistic-nominalistic controversy.[184:5] A large part of the logical discussion in the Platonic dialogues is an outgrowth of the earlier "eristic," a form of disputation in favor with the sophists, and consisting in the adroit use of ambiguity.[184:6] It is natural that in its first conscious self-criticism thought should discover the need of definite terms. The perpetual importance of definition has been largely due to the great prestige in modern philosophy of the method of geometry, which was regarded by Descartes and Spinoza as the model for systems of necessary truth.

Self-evidence is the principle according to which conviction of truth follows directly from an understanding of meaning. In the practice of his intellectual midwifery, Socrates presupposed that thought is capable of bringing forth its own certainties. And rationalism has at all times regarded truth as ultimately accredited by internal marks recognizable by reason. Such truth arrived at antecedent to acquaintance with instances is called a priori, as distinguished from a posteriori knowledge, or observation after the fact. There can be no principles of self-evidence, but logicians have always been more or less concerned with the enumeration of alleged self-evident principles, notably those of contradiction and identity. A philosophical interest in the mathematical method has led to a logical study of axioms, but with a view rather to their fruitfulness than their intrinsic truth. Indeed, the interest in self-evident truth has always been subordinate to the interest in systematic truth, and the discovery of first principles most commonly serves to determine the relative priority of definite concepts, or the correct point of departure for a series of inferences.

The greater part of the famous Aristotelian logic consists in a study of inference, or the derivation of new knowledge from old knowledge. Aristotle sought to set down and classify every method of advancing from premises. The most important form of inference which he defined was the syllogism, a scheme of reasoning to a conclusion by means of two premises having one term in common. From the premises "all men are mortal" and "Socrates is a man," one may conclude that "Socrates is mortal." This is an instance not only of the syllogism in general, but of its most important "mood," the subsumption of a particular case under a general rule. Since the decline of Aristotle's influence in philosophy there has been a notable decrease of interest in the different forms of inference; though its fundamental importance as the very bone and sinew of reasoning or deductive thinking has never been challenged. Its loss of preëminence is in part due to the growth of empiricism, stimulated by the writings of Lord Bacon in the seventeenth century, and fostered by the subsequent development of experimental science.

Observation is the fundamental logical principle of empiricism. For a radical empiricism, knowledge would consist of descriptive generalizations based upon the summation of instances. That branch of logic which deals with the advance from individual instances to general principles, is called inductive logic. It has resulted in the announcement of canons of accuracy and freedom from preconception, and in the methodological study of hypothesis, experiment, and verification. Rules for observation directed to the end of discovering causes, constitute the most famous part of the epoch-making logic of J. S. Mills.[187:7]

Present Tendencies. Theory of the Judgment.

§ [77]. There are two significant tendencies in contemporary logic. Theories of the judgment have arisen in the course of an attempt to define the least complexity that must be present in order that thought shall come within the range of truth and error. It is evident that no one either knows or is in error until he takes some attitude which lays claim to knowledge. Denoting by the term judgment this minimum of complexity in knowledge, an important question arises as to the sense in which the judgment involves the subject, predicate, and copula that are commonly present in its propositional form.

Priority of Concepts.