4.10 No more rules

That's it, there are no more basic rules. Well, there still exist some more to deal with quantifiers and two about true and false, which I will explain later, but with the former 9 we're able to try to prove the validity of any sequent in this document (except the ones with quantifiers...).

Remember again that there are no more rules: you can't change from $A\vee\neg A$ to $\blacksquare$ (true) directly, or from $\neg(A\vee B)$ to $\neg A\wedge\neg B$, nor use the distributive, associative or commutative property. You have to proceed always step by step; even the simple changes aren't allowed (currently). Why? Because probably they aren't that simple: you will understand it when having to prove things like that $A\vee\neg A$ is always true... (it's in the next section).