This chapter presents the well-formedness conditions for predicate logic and the distinction between open and closed sentences in predicate logic. We start to play with infinity, and we continue working on logical writing. There are teasers to sections on the web discussing the Busy Beaver problem in computer science and finite state automata in linguistics.

Formal topics:

• Well-formed formulas
• Open and closed wffs

Informal topics:

• A first pass at writing arguments

Supplementary topics:

• W. S. Gilbert and paradox
• Roger's paradox
• The busy beaver problem
• Finite state automata
• Puzzles