St. Augustine discusses signs and how they are used to convey meaning. He distinguishes between natural signs, like smoke indicating fire, which convey information unconsciously, and conventional signs, like words, which are used intentionally to communicate thoughts and ideas between people. While some signs address the senses of sight, sound, taste and touch, words are the most common and versatile signs used by humans to indicate what is in their minds. Signs can also be proper names that directly signify their meaning, or figurative signs where the thing named represents something else.