Any utterance, however fragmentary, must be linguistically intelligible and unambiguous. Participants in an ideal speech situation must be authentically present to one another in anticipation of forging an interpersonal connection with the goal of finding some shared understanding. To this end, speakers must be truthful and sincere and ready to act based on obligations resulting from any emergent consensus.

German Philosopher and Critical Theorist
[1929- ]
Whoever makes use of a natural language in order to come to an understanding with an addressee about something in the world is required to take a performative attitude and commit herself to certain presuppositions. In seeking to reach an understanding, natural-language users must assume, among other things, that the participants pursue their illocutionary goals without reservations, that they tie their agreement to the intersubjective recognition of criticizable validity claims, and that they are ready to take on the obligations resulting from consensus.
According to Habermas (1979: 2) “anyone acting communicatively must, in performing any speech action, raise universal validity claims and suppose they can be vindicated [or redeemed].” The first of the four claims is “comprehensibility”: the need for participants to “ascribe identical meanings to expressions.” This self-evident claim is obviously context-dependant. Beyond this, a background of consensus depends on “the implicit mutual recognition” of three “context-transcending” validity claims; namely: the truth, the truthfulness and the normative rightness of what we say.
Habermas, Jürgen (1979) Communication and the Evolution of Society. Tranlated by Thomas McCarthy. Boston. Beacon Press.
Habermas, Jürgen (1996) Between Facts and Norms: Contributions to a Discourse Theory of Law and Democracy. Translated by William Rehg. Cambridge, MA. The MIT Press.