Chapter 4: Of Speech
Chapter 5: Of Reason, and Science
Speech was invented, according to Hobbes, for the purpose of putting mental discourse into verbal discourse. There are two benefits gained by this transformation of the mental into the verbal: First, words register a train of thoughts by giving name to the thoughts' conclusions, which can then be remembered without having to reconstruct the train of thoughts continually; second, mental discourse can thus be communicated to other people.
Hobbes identifies four uses of speech: 1) To record knowledge gained of things, which is the acquisition of Arts; 2) To communicate this knowledge to others, which is Counseling or Teaching; 3) To communicate intentions and desires to others and elicit their help; and 4) To entertain ourselves by playing with words.
Hobbes also identifies four abuses of speech: 1) Inconstant signification, in which we carelessly let the meanings of words shift; 2) Metaphorical language, in which we use certain words to mean other words in order to deceive; 3) Lies; and 4) Language employed to injure other people.
Speech is defined in Hobbes's terms as "consisting of Names or Appellations, and their Connexion." Truth and falsehood, which cannot exist outside of speech, are consequent upon the nature of the connection made between names. Truth "consisteth in the right ordering of names in our affirmations," and thus to speak truly--in other words, to speak philosophically--one must use the precise and proper meanings of names. But Hobbes recognizes that we must have some foundational reference for determining whether a meaning is proper and suggests that, following the geometric method, true speech begin by gaining general acceptance of the definitions of its terms. He writes, "In Geometry (which is the onely Science that it hath pleased God hitherto to bestow upon mankind), men begin at settling the significations of their words; which settling of significations, they call Definitions; and place them at the beginning of their reckoning."
Hobbes believes that geometry is a venerable model for a philosophical language because geometry finds its stability in defined terms that everyone has agreed to recognize; therefore, geometric arguments are indisputable. It follows, then, that once philosophical definitions, or first principles, are established, true conclusions can be made by building logically upon prior claims. It is society that determines these first principles of philosophical discourse and true speech, but Hobbes is still faced with the problem of how to achieve social consent for the meanings of words.