ABSTRACT
Formal proofs help us to develop reasoning skills and are a convenient way to test arguments of various systems. From now on, formal proofs will be our main method of testing arguments.
A formal proof breaks a complicated argument into a series of small steps. Since most steps are based on our S-and I-rules (see Sections 3.10-13), you may want to review these now and then as you learn to do formal proofs.
