green numbers give full details.     |    back to list of philosophers     |     unexpand these ideas

### Ideas of Engelbretsen,G/Sayward,C, by Text

#### [, fl. 2011, two professors of logic.]

 2011 Philosophical Logic: Intro to Advanced Topics
 Intro p.2 13849 Classical logic rests on truth and models, where constructivist logic rests on defence and refutation Full Idea: Classical logic rests on the concepts of truth and falsity (and usually makes use of a semantic theory based on models), whereas constructivist logic accounts for inference in terms of defense and refutation. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Intro) A reaction: My instincts go with the classical view, which is that inferences do not depend on the human capacity to defend them, but sit there awaiting revelation. My view isn't platonist, because I take the inferences to be rooted in the physical world.
 7 p.132 13852 Axioms are ω-incomplete if the instances are all derivable, but the universal quantification isn't Full Idea: A set of axioms is said to be ω-incomplete if, for some universal quantification, each of its instances is derivable from those axioms but the quantification is not thus derivable. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 7)
 8 p.142 13913 The four 'perfect syllogisms' are called Barbara, Celarent, Darii and Ferio Full Idea: There are four 'perfect syllogisms': Barbara (every M is P, every S is M, so every S is P); Celarent (no M is P, every S is M, so no S is P); Darii (every M is P, some S is M, so some S is P); Ferio (no M is P, some S is M, so some S is not P). From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) A reaction: The four names are mnemonics from medieval universities.
 8 p.143 13914 Syllogistic logic has one rule: what is affirmed/denied of wholes is affirmed/denied of their parts Full Idea: It has often been claimed (e.g. by Leibniz) that a single rule governs all syllogistic validity, called 'dictum de omni et null', which says that what is affirmed or denied of any whole is affirmed or denied of any part of that whole. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) A reaction: This seems to be the rule which is captured by Venn Diagrams.
 8 p.144 13915 Syllogistic can't handle sentences with singular terms, or relational terms, or compound sentences Full Idea: Three common kinds of sentence cannot be put into syllogistic ('categorical') form: ones using singular terms ('Mars is red'), ones using relational terms ('every painter owns some brushes'), and compound sentences. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8)
 8 p.146 13916 Term logic uses expression letters and brackets, and '-' for negative terms, and '+' for compound terms Full Idea: Term logic begins with expressions and two 'term functors'. Any simple letter is a 'term', any term prefixed by a minus ('-') is a 'negative term', and any pair of terms flanking a plus ('+') is a 'compound term'. Parenthese are used for grouping. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) A reaction: [see Engelbretsen and Sayward for the full formal system]
 Ch.2 p.50 13850 In modern logic all formal validity can be characterised syntactically Full Idea: One of the key ideas of modern formal logic is that all formally valid inferences can be specified in strictly syntactic terms. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Ch.2)
 Ch.3 p.70 13851 Unlike most other signs, = cannot be eliminated Full Idea: Unlike ∨, →, ↔, and ∀, the sign = is not eliminable from a logic. From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Ch.3)