Write one premise per line in plain English or symbols (∧ ∨ → ↔ ¬ ∀ ∃). The formal reading appears under each line; the key on the right says what each letter stands for.
Start a line with Therefore, (or press ∴ conclusion) to mark the conclusion — validity is checked as you type.
Choose the logic: Categorical for A/E/I/O syllogisms, Propositional for sentence letters, Predicate for quantifiers, names, and relations.
Prove a step by citing lines and a rule at the end of it: (1, 2 MP). The abbreviations are listed under Reference; a chip shows ✓ when the step follows by that rule. Click a chip to edit it.
Tab indents a line into a sub-premise, Shift+Tab backs out, Esc leaves the writing surface, Ctrl+Z / Ctrl+Y undo and redo.
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Enter new premiseTab sub-premiseShift+Tab back outEsc leave the writing surfacetype “Therefore, …” to mark the conclusionBackspace undoes a symbol swapcite a step: (1, 2 MP) at the end of a line — click the tag to edit