Lecture #16 continued our look at propositional logic. In particular it looked at proof theory.
Notes are available in four formats:
At this point you should be able to tackle Chapter 13 of the textbook, so read it through.
As I said during class, the only way you will get good at doing proofs (and they are the kind of thing which have a habit of cropping up in exams) is by working through ones done by other people and doing them yourselves.
So, you should go through the examples in the notes carefully (and then look at the homework and tutorial examples).
Finally, if you weren't completely bored by my description of Lewis Carroll's Dialogue between Achilles and the Tortoise, you might like to read it.