The Commens Dictionary
Quote from ‘Definitions for Baldwin's Dictionary [R]’
…in a narrower sense, logic is the science of the reference of symbols to their objects. For logic in this narrower sense, all symbols which have precisely the same possible objects […] are identical, – a limitation which must not be overlooked. Hence, according to Boole, and those who follow him, every symbol has one or other or two values, according as it does or does not […] represent the object intended.