Which part do you disagree with? Do you think that the conclusion is true or do you think that the premise is true even though the conclusion is false? — Michael
If I'm not a cat then I can't be a cat
Therefore, if I can be a cat then I am a cat. — Isaac
If I'm not a cat, I can't possibly be a cat. I could have been, but I cannot actually be at the same time as I'm not. — Isaac
Are you saying it's possible to be x at the same time as not being x? — Isaac
1 and 3 are false, 2 and 4 are true. — Michael
The problem here is with using modal logic terms together with knowledge — Isaac
I think it is "could have been wrong" not "could be wrong" the latter is a contradiction. — Janus
But what does "necessarily true" mean? — Janus
If p is necessarily true it is not possible that p could have been false. If p is true is it is not possible that p is false, but it is possible that p could have been false. — Janus
I thought the very basis of modal logic is that contingent truths, which cannot be false (obviously) could have been false (which means could be false in other possible worlds). — Janus
No, it's just saying something like "aliens exist" is not necessarily true, therefore it's possibly true and possibly false. — Michael
If "aliens exist" is true, then "aliens exist" cannot be false — Janus
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