Heresy is a word which, when it is used without passion, signifies a private opinion. So the different sects of the old philosophers, Academians, Peripatetics, Epicureans, Stoics, &c., were called heresies.
Thomas HobbesThe first author of speech was God himself, that instructed Adam how to name such creatures as He presented to his sight.
Thomas HobbesThe Imagination that is raised in man (or any other creature imbued with the faculty of imagining) by words, or other voluntary signs, is that we generally call Understanding; and is common to Man and Beasts.
Thomas HobbesThey that approve a private opinion, call it opinion; but they that dislike it, heresy; and yet heresy signifies no more than private opinion.
Thomas Hobbes