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TFL

FOL

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Proof:

Select if TFL or FOL syntax:Premises (separate with “,” or “;”):Conclusion:

Sample exercise sets

Instructions

TFL atomic sentences:

(single uppercase letters) A, B, X, etc. FOL atomic sentences:

(single uppercase letters other than A or E followed by

lowercase letters a–w without parentheses, or identities) Pa, Fcdc, a = d, etc. For negation you may use any of the symbols: ¬ ~ ∼ - − For conjunction you may use any of the symbols: ∧ ^ & . · * For disjunction you may use any of the symbols: ∨ v For the biconditional you may use any of the symbols: ↔ ≡ <-> <> (or in TFL only: = ) For the conditional you may use any of the symbols: → ⇒ ⊃ -> > For the universal quantifier (FOL only), you may use any of the symbols: ∀x (∀x) Ax (Ax) (x) ⋀x For the existential quantifier (FOL only), you may use any of the symbols: ∃x (∃x) Ex (Ex) ⋁x For a contradiction you may use any of the symbols: ⊥ XX #

The following buttons do the following things:

× = delete this line = add a line below this one = add a new subproof below this line = add a new line below this subproof to the parent subproof = add a new subproof below this subproof to the parent subproof

Apart from premises and assumptions, each line has a cell immediately to its right for entering the justifcation. Click on it to enter the justification as, e.g. “&I 1,2”.

Hopefully it is otherwise more or less obvious how to use it.