List of rules
Introduction
| Symbol | Reads | Argument Semantics |
|---|---|---|
| ^I | And Introduction | from x, y deduce x ^ y |
| ->I | Implication Introduction | from "assuming x deduces y", deduce x -> y |
| /I | Or Introduction | from x deduce x / ? or ? / x |
| ~I | Not Introduction | from "assuming original deduces bottom" deduce its negation |
| ~~I | Double Negation Introduction | from x deduce ~~x |
| FI | Falsity Introduction | from x and ~x deduce F |
| TI | Truth Introduction | from nothing deduces T (but why would you do that 😏) |
| <->I | Equivalence Introduction | from x -> y and y -> x deduce x <-> y |
| existsI | Exists Introduction | from 𝝓(x) deduce ∃a 𝝓(a) |
| forallI | Forall Introduction | from "c deduces f(c)" deduce ∀x f(x) |
Elimination
| Symbol | Reads | Argument Semantics |
|---|---|---|
| ^E | And Elimination | from x ^ y deduce x (or y) |
| ->E | Emplication Elimination | from x -> y and x deduce y |
| /E | Or Elimination | from x1 / x2, "assuming x1 deduces y", "assuming x2 deduces y", deduce y |
| ~E | Not Elimination | from x and ~x deduces F (same as FI) |
| ~~E | Double Negation Elimination | from ~~x deduce x |
| FE | Falsity Elimination | from F deduce anything |
| <->E | Equivalence Elimination | from x <-> y and either side, deduce the other side |
| existsE | Exists Elimination | from ∃a 𝝓(a) and "𝝓(c) for some c deduces x", deduce x |
| forallE | Forall Elimination | from ∀x f(x) deduce f[x/c] |
| forall->E | Forall Implication Elimination | from ∀x f(x) -> g(x) and f(c), deduces g(c) |
Special
| Symbol | Reads | Argument Semantics |
|---|---|---|
| LEM | Law of Excluded Middle | from nothing deduce p / ~p |
| MT | Modus Tollens | from x -> y and ~y, deduce ~x |
| PC | Proof by Contradiction | from "assuming x deduces F", deduce ~x |
| refl | rule of Reflection | from nothing deduce x = x |
| =sub | Equality Substitution | from a = b and f(a), deduce f(b) |
| sym | rule of Symmetry | from a = b deduce b = a |
| forall I const | forall I const | introduces a new free variable |
| given | Given | given proposition / formula |
| premise | Premise | given proposition / formula |
| ass | Assumption | assume proposition / formula |
| tick | Tick | from x deduce x (syntactic flag) |