Combining Texts

All the ideas for 'Good and Evil', 'An Introduction to Modal Logic' and 'First-order Logic, 2nd-order, Completeness'

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15 ideas

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL

9540	A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0 [Hughes/Cresswell]

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL

9541	The Law of Transposition says (P→Q) → (¬Q→¬P) [Hughes/Cresswell]

4. Formal Logic / B. Propositional Logic PL / 4. Soundness of PL

9543	The rules preserve validity from the axioms, so no thesis negates any other thesis [Hughes/Cresswell]

5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic

10757

Henkin semantics has a second domain of predicates and relations (in upper case) [Rossberg]

10751

Second-order logic needs the sets, and its consequence has epistemological problems [Rossberg]

10759

There are at least seven possible systems of semantics for second-order logic [Rossberg]

5. Theory of Logic / B. Logical Consequence / 2. Types of Consequence

10753

Logical consequence is intuitively semantic, and captured by model theory [Rossberg]

5. Theory of Logic / B. Logical Consequence / 3. Deductive Consequence |-

10752

Γ |- S says S can be deduced from Γ; Γ |= S says a good model for Γ makes S true [Rossberg]

5. Theory of Logic / E. Structures of Logic / 1. Logical Form

10754

In proof-theory, logical form is shown by the logical constants [Rossberg]

5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models

10756

A model is a domain, and an interpretation assigning objects, predicates, relations etc. [Rossberg]

5. Theory of Logic / J. Model Theory in Logic / 2. Isomorphisms

10758

If models of a mathematical theory are all isomorphic, it is 'categorical', with essentially one model [Rossberg]

5. Theory of Logic / K. Features of Logics / 4. Completeness

10761

Completeness can always be achieved by cunning model-design [Rossberg]

9544	A system is 'weakly' complete if all wffs are derivable, and 'strongly' if theses are maximised [Hughes/Cresswell]

5. Theory of Logic / K. Features of Logics / 5. Incompleteness

10755

A deductive system is only incomplete with respect to a formal semantics [Rossberg]

22. Metaethics / C. The Good / 1. Goodness / a. Form of the Good

22489

'Good' is an attributive adjective like 'large', not predicative like 'red' [Geach, by Foot]