Book Three discusses how to interpret ambiguous literal and ambiguous figurative signs. Ambiguous signs are those whose meaning is unclear or confused. He suggests first determining things from signs. Then, once the distinction is made, understand the literal meaning of the text (things as things, nothing more). Determining if there is a deeper meaning in the text can be done by recognizing a different, more figurative, mode of writing. This may show that the things are also signs of something else. For example, an aged tree could be a literal tree or it could be a symbol of long life (as a sign or allegory).