10/3/08 10 Software under construction.
a) P⊃ Q, R⊃ Q ∴ (P∨ R)⊃ Q
b) P⊃ (Q∧R), ¬R ∴ ¬P
c) ∴ ((P⊃ Q)⊃ Q)⊃ Q
d) ∴ ((P⊃ Q)∧ (¬P⊃ Q))⊃ ¬P
Roll your own
Type your own entries into the next applet. The applets can be configured to run a variety of symbol systems. This particular one is running those of Priest's book, so use these symbols for the logical connectives.
F ∴ F ∧ G ¬ ∧ ∨ ⊃ ≡ ∀ ∃ ∴ □ ◊
You need a list of zero or more premises, separated by commas, then a therefore, and then the conclusion. Use this as a template
P, Q, R ∴ S
If you are really giving this a good workout.... There is a puzzling little trap here that sometimes occurs (but rarely). When you copy and paste, or drag and drop, html text across browsers, desktops, etc., crossing from one application to another, your computer sometimes adds an extra invisible character which marks the end of the text. You cannot see that character, but the logic software parsing formulas certainly can. So sometimes the logic software may tell you that an apparently good formula is not well formed. If trailing invisible characters seem to be an issue, one workaround is to put the insertion point after the formula and hit backspace or delete (that will delete the invisible character).