Hey, this may be a dumb question but I just am not getting it. Every time I try to write it myself I've switched it or something, but it's not what is written when the answer is explained. I got most confused at question 5, because when writing the contrapositive the man in the video said "just reverse and negate it", but he has also emphasized multiple times that you cannot just reverse a premise to get the contrapositive. Further, sometimes it isn't switched, the premise will be diagrammed the same way, except both sides are crossed out. I'm not sure if this made any sense and I can definitely elaborate further if needed- I just am not getting it.
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This isn't a dumb question! Contrapositives can be tricky to learn for most people, especially because they are completely unfamiliar unless you have a background in formal logic.
You're correct that for contrapositives we reverse and negate them.
Some examples: Original statement: A -> B Contrapositive: Not B -> Not A
Original statement: If it's raining, then I will stay home Contrapositive: If I don't stay home, then it's not raining
Original statement: if fish -> has gills Contrapositive: No gills -> Not fish
I think what the video is getting at with the idea that we can't just reverse the contrapositive, is we CANNOT do something like this:
If fish then has gills Contrapositive: If not a fish then no gills.
That doesn't work because we didn't reverse them!
I hope this helps, let us know if you have any further questions. If you're still confused about any specific contrapositives, examples, or places in the video, we can also help with that.
