Regarding ‘dialogue’ as a normative rather than a purely descriptive concept, this study describes the rhetoric of practical arguments about the possibility or impossibility of dialogue in a corpus of discourse samples primarily drawn from the Internet. Political, social, and personal domains of dialogue are distinguished and associated respectively with realist, moral, and experiential discourses that intermix in practical argumentation. Arguments for or against the possibility of dialogue may appeal to objective conditions (convergence of interests or beliefs, relatively equal power, a just and supportive sociopolitical order) as well as to morally accountable attitudes and actions (respect, trust, and reaching out versus hatred, dogmatism, dishonesty, and violence). Arguments may also appeal to critical events that interrupt routine patterns of thought and communication and are said to open a potential for dialogue that may or may not be realized in practice. Implications for normative theories of dialogue and rhetoric are considered.