I wish that anyone trying to teach logic would emphasise that there are many, many possible formal systems for any particular logic, and there is absolutely no

I wish that anyone trying to teach logic would emphasise that there are many, many possible formal systems for any particular logic, and there is absolutely no standard. That way, confused readers won't end up on places like /r/logic asking "how do I formally prove this proposition in logic?" only to be told "we don't know what formal system you're using [and we don't even know what logic]." Or worse, readers will go on to write their own blog post telling more readers that the one system they happened to learn is the extent of logic. So don't do this: > there are 10 rules of inference that we can use in proving the validity of arguments https://philonotes.com/index.php/2018/03/28/rules-of-inference/ https://philonotes.com/index.php/2018/03/28/rules-of-inferen... If there were just 10 rules of inference in logic, that would be really cool to know. But there aren't. There are infinitely many rules of inference, and many different minimal sets can be appropriately chosen from which to derive all the others. Once you realise that, a random selection like the one on this page simply isn't interesting at all. In fact, the choice here looks like a bunch of historical remnants inelegantly thrown together. For comparison, this is a bit like writing a blog called "what is programming", and then going straight into the syntax and semantics of, say, Pascal as if it's the only programming language. If you don't understand the difference between programming and Pascal, I'd advise you don't write a blog called "What is programming?" The same applies with logic, and given some of the author's other fairly substantial technical misunderstandings, my advice is to try a different resource for this topic.