Much contemporary political discourse in the US and industrialized west is defective. According to a number of scholars, such as Scott Aikin and Robert Talisse, this defectiveness can plausibly be explicated in terms of a breakdown in political civility. In this thesis, I scrutinize possible explanations for why incivilities are widespread in political discourse. My goal is to defend an explanation according to which citizen incivility in political discourse is blameless. To do this, I appeal to a principle of reciprocity. According to the principle of reciprocity, citizens are not required to maintain civility in political discourse if they have reason to believe that their interlocutors will not reciprocate civility. When applied to contemporary politics, this principle implies that ordinary citizens in democratic societies across the US and industrialised west are often justified in being uncivil in political debate. For these citizens often have no reason to believe that their interlocutors will be civil. If the reciprocity principle is right, then policies aimed at restoring civility in political discourse must be concerned to build citizen trust that others will reciprocate civility. Without this trust, citizens may not see themselves as having reason to be civil. The thesis is divided into two chapters. In chapter 1, I defend the justificatory account of incivility against two competing accounts of political incivility—identity and group theories. These accounts pathologize political incivility as a kind of irrationality, but based on the argument from reciprocity, I argue that political incivilities are often rational and so justified. In chapter 2, I analyse the kind of trust that is necessary to build more civility in political discourse. In particular, I develop and defend a conception of deliberative trust, which is defined as the belief that one’s interlocutor will reciprocally adhere to the norms of civility. / Thesis / Master of Arts (MA) / In this thesis, I scrutinize possible explanations for why incivilities are widespread in contemporary political discourse. By appeal to a principle of reciprocity, my ultimate goal is to defend an explanation according to which citizen incivility in political discourse is blameless. According to the principle of reciprocity, citizens are not required to maintain civility if they have reason to believe that their interlocutors will not reciprocate civility in political discussion. Based on this principle, I argue that ordinary citizens in democratic societies across the US and industrialised west are often justified in being uncivil in political debate. For these citizens often have no reason to believe that their interlocutors will be civil. If the justificatory account of incivility is on the right track, then policies aimed at restoring civility in political discourse must be concerned to build citizen trust that others will reciprocate civility. Without this trust, citizens may not see themselves as having reason to be civil in political debate.