The third and last kind of representations are symbols or general representations. They connote attributes and so connote them as to determine what they denote. To this class, belong all words and all conceptions. Most combinations of words are also symbols. A proposition, an argument, even a whole book may be, and should be, a single symbol.
http://www.commens.org/dictionary/entry/quote-lowell-lectures-logic-science-or-induction-and-hypothesis-lecture-vii