First principles

The first principles (the first principles of Being and thought, the highest laws of thought and cognition) - in logic and traditional metaphysics, the set of logical laws, which were thought to be the most obvious of all possible theorems, are independent of other statements (do not give to derive from any other logical law) and constitute the ultimate justification for all the laws of logic. They included the principle of identity, the principle of contradiction and the principle of the excluded measure. The dictum de omni et nullo and the principle of rationality were also often included in them. Most of these laws formulated (not always in mature and full form) Aristotle, who - although convinced of their particular importance - did not separate them together as "first principles." This was done only by medieval logic, from which the conviction of the existence of the "first principles" went back to the modern logic.

Modern logic rejects the notion of "first principles." The concept of clarity was considered too vague to build logical systems on it. Furthermore, the logical rules regarded as "first principles" are neither independent nor justified by all other laws of logic. A kind of counterpart of the "first principles" is, in modern logic, the notion of an "axiom" - the rules recognized in traditional logic as "first" can not, however, constitute the axiom of the propositional calculus or any deductive system. They are theorems that are derived from the axioms of the propositional calculus by means of a number of evidence steps. There are also attempts at the "first principles" not as the first logical principle, but as the first principles of metaphysics (sometimes also as the first principles of thinking in the psychological sense). They are especially on the ground of neotomism, where they are considered as specific rules of metaphysics. Bibliography

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