4 ideas
13342 | Carnap defined consequence by contradiction, but this is unintuitive and changes with substitution [Tarski on Carnap] |
13251 | Each person is free to build their own logic, just by specifying a syntax [Carnap] |
22312 | Facts can be both positive and negative [Wittgenstein, by Potter] |
12693 | A body is that which exists in space [Leibniz] |