Abstract
It is well known that no consistent normal modal logic contains (as theorems) both ♦A and ♦A (for any formula A). Here we observe that this claim can be strengthened to the following: for any formula A, either no consistent normal modal logic contains ♦ A, or else no consistent normal modal logic contains ♦-A.
Original language | English |
---|---|
Pages (from-to) | 25 - 31 |
Number of pages | 7 |
Journal | Bulletin of the Section of Logic |
Volume | 44 |
Issue number | 1-2 |
Publication status | Published - 2015 |