This thesis treats Mulligan as characteristic of mocker, betrayer and pretender. Each figure corresponds to Stephen`s three masters or nooses― Ireland`s church, politics, and home respectively, which leads to his being a characterization of the nightmare of history. That is why he is described as a spirit of denial. Confronted with Stephen at the first chapter of Ulysses, it is supposed that he haunt the subsequent part of the work as the motif of nightmarish history. It is through his characterization that Joyce exerts his realistic imagination for Irish realities and achieves a universal pattern of life as the process of trying to awake from the nightmare of history.