BASIC TABLES
| P | Q | ~Q | P • Q | P ∨ Q | P ⊃ Q | P ≡ Q |
| T | T | F | T | T | T | T |
| T | F | T | F | T | F | F |
| F | T | F | F | T | T | F |
| F | F | T | F | F | T | T |
BEST STARTING PLACES
Premises with forms:
P ~P P•Q
Conclusions with forms:
P ~P P∨Q P⊃Q
The values in the boxes are the goals for which you are striving. If you can meet each of them, then the argument is INVALID.
Start with an argument part, a premise or the conclusion, whose assigned truth value can be met in only one way such as a premise with a • MAIN OPERATOR (since there is only one true line in its basic table) or a conclusion with a ⊃ MO (since there is only one false row in its table).
If the values are forced in this way and a goal canNOT be met, the argument is VALID. If no goal can only be met in one way, pick any goal and create enough lines to check EACH way it can be met.
Every VALID argument has a MO value which contradicts the assignment. In the text these are shown inside an oval. If one part on a line is contradictory, the whole line is done and work should continue with the other lines.