 In the summative sense, collective self-deception refers to self-deceptive belief shared by a group of individuals, who each come to hold the self-deceptive belief for similar reasons and by similar means, varying according to the account of self-deception followed. We might call this self-deception across a collective. In the non-summative sense, the subject of collective self-deception is the collective itself, not simply the individuals comprising it. The following sections offer an overview of these forms of collective self-deception, noting the significant challenges posed by each.