Category
page 2Mathematical logic
König's theorem
theorem
complete theory
consistent theory where every statement is provable or disprovable
Löb's theorem
theorem
reverse mathematics
Branch of mathematical logic
subitizing
thumb|An observer may be able to instantly judge how many red circles are present without counting them, but would find it harder to do so for the greater number of blue circles.
Subitizing is the rapid, accurate, and effortless ability to perceive small quantities of items in a set, typically when there are four or fewer items, without relying on linguistic or arithmetic processes. The term refers to the sensation of instantly knowing how many objects are in the visual scene when their number falls within the subitizing range.
Dedekind number
combinatorial sequence of numbers
diagonal lemma
Statement in mathematical logic
vacuous truth
statement that can be expressed in the form of a conditional statement with a false antecedent
special case
specific, usually well-known application of a mathematical rule or law
impredicativity
In mathematics, logic and philosophy of mathematics, something that is impredicative is a self-referencing definition. Roughly speaking, a definition is impredicative if it invokes (mentions or quantifies over) the set being defined, or (more commonly) another set that contains the thing being defined. There is no generally accepted precise definition of what it means to be predicative or impredicative. Authors have given different but related definitions.
type
term in model theory and related areas of mathematics
Brouwer–Heyting–Kolmogorov interpretation
interpretation of intuitionistic logic
Conservative extension
area of research
semantic theory of truth
in the philosophy of language, a theory of truth holding that truth is a property of sentences
Class logic
definable set
n-ary relation on the domain of a structure whose elements satisfy some formula in the
turnstile
mathematical symbol
Lindenbaum's lemma
double turnstile
mathematical symbol
non-standard model of arithmetic
model of (first-order) Peano arithmetic that contains non-standard numbers
Craig interpolation
theorem
Herbrand interpretation
simple logical interpretation
Lindström's theorem
Theorem in mathematical logic

Laws of Form
1969 non-fiction book by G. Spencer-Brown
T-schema
The T-schema ("truth schema", not to be confused with "Convention T") is used to check if an inductive definition of truth is valid, which lies at the heart of any realisation of Alfred Tarski's semantic theory of truth. Some authors refer to it as the "Equivalence Schema", a synonym introduced by Michael Dummett.
absoluteness
in mathematical logic, property of formula that has the same truth value in each of some class of structures
ground expression
logical expression whose terms do not contain any variables
hypostatic abstraction
formal operation that transforms a predicate into a relation
Boolean differential calculus
subject field of Boolean algebra discussing changes of Boolean variables and functions
substructure
subset of a structure that itself forms a structure
Herbrand structure
structure over a vocabulary defined solely by syntactical properties
proof of impossibility
result demonstrating that a particular problem cannot be solved as described in the claim, or that a particular set of problems cannot be solved in general
diagram
given a model of a theory over a 1st-order language, the set of atomic sententences and negations thereof of that hold in the model, when the language is extended with constant symbols for each element in the domain in the model
structuralism
viewpoint in the philosophy of mathematics
Rosser's trick
method in mathematical logic