excluded middle
41Constructive proof — In mathematics, a constructive proof is a method of proof that demonstrates the existence of a mathematical object with certain properties by creating or providing a method for creating such an object. This is in contrast to a nonconstructive… …
42Propositional formula — In propositional logic, a propositional formula is a type of syntactic formula which is well formed and has a truth value. If the values of all variables in a propositional formula are given, it determines a unique truth value. A propositional… …
43Impossible world — In philosophical logic, the concept of an impossible world (sometimes non normal world) is used to model certain phenomena that cannot be adequately handled using ordinary possible worlds. An impossible world, w, is the same sort of thing as a… …
44Diaconescu's theorem — In mathematical logic, Diaconescu s theorem, or the Goodman–Myhill theorem, states that the full axiom of choice is sufficient to derive the law of the excluded middle, or restricted forms of it, in constructive set theory. It was discovered in… …
45Russell's paradox — Part of the foundations of mathematics, Russell s paradox (also known as Russell s antinomy), discovered by Bertrand Russell in 1901, showed that the naive set theory of Frege leads to a contradiction.It might be assumed that, for any formal… …
46Luitzen Egbertus Jan Brouwer — [ˈlœyt.sən ɛx.ˈbɛʁ.təs jɑn ˈbʁʌu.əʁ] (February 27 1881, Overschie – December 2 1966, Blaricum), usually cited as L. E. J. Brouwer but known to his friends as Bertus, was a Dutch mathematician and philosopher, a graduate of the University of… …
47Preintuitionism — In some circles of mathematical philosophy the Pre Intuitionists are considered to be a small but influential group who informally shared similar philosophies on the nature of mathematics. The term itself was used by L. E. J. Brouwer, who in his… …
48Law of noncontradiction — This article uses forms of logical notation. For a concise description of the symbols used in this notation, see List of logic symbols. In classical logic, the law of non contradiction (LNC) (or the principle of non contradiction (PNC), or the… …
49Aristotle’s logic and metaphysics — Alan Code PART 1: LOGICAL WORKS OVERVIEW OF ARISTOTLE’S LOGIC The Aristotelian logical works are referred to collectively using the Greek term ‘Organon’. This is a reflection of the idea that logic is a tool or instrument of, though not… …
50Logic and the mind — This article discusses the relationship between the formal logic and the mind.For a long time people believed that intelligence is equivalent to conceptual understanding and reasoning. A part of this belief was that the mind works according to… …
