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Oh Yeah? Well, Prove It.
Oh Yeah? Well, Prove It.

... unproven assumptions that are the foundation of all mathematics. (Not everyone agrees on what axioms should be used, but that’s a whole other story.) These basic axioms are combined using the rules of logic into more complicated statements called theorems. If the axioms are true and the logic is sou ...
The Logic of Atomic Sentences
The Logic of Atomic Sentences

... We are told that b is to the right of c. So c must be to the left of b, since right of & left of are inverses of each other. And since b = d, c is left of d by the Indiscernibility of Identicals. But we are also told that d is left of e, and consequently c is to the left of e, by the textbftransitiv ...
Nonmonotonic Logic II: Nonmonotonic Modal Theories
Nonmonotonic Logic II: Nonmonotonic Modal Theories

Logic as a Tool 3mm Chapter 2: Deductive Reasoning in
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... Alternatively, after finitely many applications of the Propositional Resolution rule, no new applications of the rule remain possible. If the empty clause is not derived by then, it cannot be derived at all, and hence the A1 , . . . , An and ¬B can be satisfied together, so the logical consequence A ...
Frege, Boolos, and Logical Objects
Frege, Boolos, and Logical Objects

... Frege’s program was undermined by the inconsistency of Basic Law V with second-order logic. Recently, there has been a renaissance of research on consistent Frege-style systems.2 In an important series of papers, George Boolos also developed systems for reconstructing Frege’s work. We’ll focus on th ...
On the Construction of Analytic Sequent Calculi for Sub
On the Construction of Analytic Sequent Calculi for Sub

... Γ and ∆ are finite sets of formulas. We employ the standard sequent notations, e.g. when writing expressions like Γ, ψ ⇒ ∆ or ⇒ ψ. The union of sequents is defined by (Γ1 ⇒ ∆1 ) ∪ (Γ2 ⇒ ∆2 ) = Γ1 ∪ Γ2 ⇒ ∆1 ∪ ∆2 . For a sequent Γ ⇒ ∆, frm(Γ ⇒ ∆) = Γ ∪ ∆. This notation is naturally extended to sets of ...
Logic: Semantics and Bottom-Up Proofs
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Paper - Department of Computer Science and Information Systems

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Chapter 2 Propositional Logic
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LINEAR LOGIC AS A FRAMEWORK FOR SPECIFYING SEQUENT
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... In this paper, we make use of linear logic as a meta-logic and find that we can specify a variety of proof systems for object-level systems. By making use of classical linear logic, we are able to capture not only natural deduction proof systems but also many sequent calculus proof systems. We will ...
Document
Document

THE HITCHHIKER`S GUIDE TO THE INCOMPLETENESS
THE HITCHHIKER`S GUIDE TO THE INCOMPLETENESS

... Now we are powerful enough to deal with elementary arithmetic, but still something is missing. Let us try to write out the following theorem as a formal sentence: Theorem 2. There is an even number which is not the sum of two prime numbers. What is a prime? A number which is no divisible by any numb ...
Hilbert`s investigations on the foundations of arithmetic (1935) Paul
Hilbert`s investigations on the foundations of arithmetic (1935) Paul

... infinite sets [Mengen] in general lose all their warranty [Berechtigung ] with the view identified above [oben gekennzeichneten Auffassung ]: we do not have to think the totality of all possible laws according to which the elements of a fundamental sequence can proceed as the set of real numbers, bu ...
Incompleteness in a General Setting
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... of a coding system representing the syntax of an object language (typically, that of arithmetic) within that same language. These details are seldom illuminating and tend to obscure the core of the argument. For this reason a number of efforts have been made to present the essentials of the proofs o ...
Introduction to Linear Logic
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Constructive Mathematics in Theory and Programming Practice
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duality of quantifiers ¬8xA(x) 9x¬A(x) ¬9xA(x) 8x¬A(x)
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... There are problems that cannot be solved by computer programs (i.e. algorithms) even assuming unlimited time and space. What is an “algorithm”? The following are all equivalent: - C programs, scheme programs, Java programs . . . - Turing machines (Turing’s idea of an “algorithm”) ...
Introduction to first order logic for knowledge representation
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... phrases of this language are used to describe objects of the real worlds, their properties, and facts that holds. This language can be informal (natural language, graphical language, icons, etc...) or a formal (logical language, programming language, mathematical language, . . . ) It is also possibl ...
Partial Grounded Fixpoints
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... groundedness for points x ∈ L. It is based on the same intuitions, but applied in a more general context. We again explain the intuitions under the assumption that the elements of L are sets of “facts” and the ≤ relation is the subset relation between such sets. In this case, a point (x, y) ∈ Lc rep ...
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Law of thought

The laws of thought are fundamental axiomatic rules upon which rational discourse itself is often considered to be based. The formulation and clarification of such rules have a long tradition in the history of philosophy and logic. Generally they are taken as laws that guide and underlie everyone's thinking, thoughts, expressions, discussions, etc. However such classical ideas are often questioned or rejected in more recent developments, such as Intuitionistic logic and Fuzzy Logic.According to the 1999 Cambridge Dictionary of Philosophy, laws of thought are laws by which or in accordance with which valid thought proceeds, or that justify valid inference, or to which all valid deduction is reducible. Laws of thought are rules that apply without exception to any subject matter of thought, etc.; sometimes they are said to be the object of logic. The term, rarely used in exactly the same sense by different authors, has long been associated with three equally ambiguous expressions: the law of identity (ID), the law of contradiction (or non-contradiction; NC), and the law of excluded middle (EM).Sometimes, these three expressions are taken as propositions of formal ontology having the widest possible subject matter, propositions that apply to entities per se: (ID), everything is (i.e., is identical to) itself; (NC) no thing having a given quality also has the negative of that quality (e.g., no even number is non-even); (EM) every thing either has a given quality or has the negative of that quality (e.g., every number is either even or non-even). Equally common in older works is use of these expressions for principles of metalogic about propositions: (ID) every proposition implies itself; (NC) no proposition is both true and false; (EM) every proposition is either true or false.Beginning in the middle to late 1800s, these expressions have been used to denote propositions of Boolean Algebra about classes: (ID) every class includes itself; (NC) every class is such that its intersection (""product"") with its own complement is the null class; (EM) every class is such that its union (""sum"") with its own complement is the universal class. More recently, the last two of the three expressions have been used in connection with the classical propositional logic and with the so-called protothetic or quantified propositional logic; in both cases the law of non-contradiction involves the negation of the conjunction (""and"") of something with its own negation and the law of excluded middle involves the disjunction (""or"") of something with its own negation. In the case of propositional logic the ""something"" is a schematic letter serving as a place-holder, whereas in the case of protothetic logic the ""something"" is a genuine variable. The expressions ""law of non-contradiction"" and ""law of excluded middle"" are also used for semantic principles of model theory concerning sentences and interpretations: (NC) under no interpretation is a given sentence both true and false, (EM) under any interpretation, a given sentence is either true or false.The expressions mentioned above all have been used in many other ways. Many other propositions have also been mentioned as laws of thought, including the dictum de omni et nullo attributed to Aristotle, the substitutivity of identicals (or equals) attributed to Euclid, the so-called identity of indiscernibles attributed to Gottfried Wilhelm Leibniz, and other ""logical truths"".The expression ""laws of thought"" gained added prominence through its use by Boole (1815–64) to denote theorems of his ""algebra of logic""; in fact, he named his second logic book An Investigation of the Laws of Thought on Which are Founded the Mathematical Theories of Logic and Probabilities (1854). Modern logicians, in almost unanimous disagreement with Boole, take this expression to be a misnomer; none of the above propositions classed under ""laws of thought"" are explicitly about thought per se, a mental phenomenon studied by psychology, nor do they involve explicit reference to a thinker or knower as would be the case in pragmatics or in epistemology. The distinction between psychology (as a study of mental phenomena) and logic (as a study of valid inference) is widely accepted.
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