You know the kid in middle school who thinks that he wants to be the President of the United States? Do you remember how irritating this kid was, how confident and self-sure he was? Well, many who want to be novelists can have the same kind of demeanor. We know a lot of smart people who had a lot of trouble with Portrait of the Artist as a Young Man not because it's hard (which it is), but because Stephen Dedalus comes across as an overly confident boy. Toward the close of the book, when he decides that he will go to Paris and pursue the life of the artist, he offers two famous lines.
The first line is: "Non serviam." In Latin, this means "I will not serve," and echoes Lucifer's statement to God in John Milton's Paradise Lost that it would be better to be a ruler in hell than to be a servant in heaven. The second is: "I go to encounter for the millionth time the reality of experience and to forge in the smithy of my soul the uncreated conscience of my race." Both of these lines come back to bite Stephen at the start of Ulysses. What is so refreshing about the start of the book is that – moody as he is – Stephen has learned a lot of humility and he has begun to mature (though he still has a long way to go).
The key thing that happens between the close of Portrait in late 1902 and the opening of Ulysses on the morning of June 16, 1904 is the death of Stephen's mother. Presumably, Stephen lived a bohemian lifestyle while he was in Paris, but he has failed to produce art, and thus has returned to Ireland as something of a failure. The most pressing reason for his return was that his mother was sick, and at her deathbed her last wish was for Stephen to pray over her. Stephen, who has cast off the Church and the end of Portrait, refuses to pray. And his mother dies with her son refusing to pray over her. Unsurprisingly, this leaves Stephen just a little moody at the start of Ulysses, and not too open to Buck Mulligan's joking about how he killed his mother.
Now there are two big thematic aspects of "Telemachus" that you want to be tuned into right from the start.
The first one is the notion of Irish-ness, and what it means to be Irish in 1904. In 1904, Ireland is still under English rule though there is a strong nationalist movement within the country. At one point Buck Mulligan begins singing some lines from W.B. Yeats's "Who Goes with Fergus?" and Stephen remembers singing these lines to his mother before she died. Yeats was the leading figure of the Irish Literary Revival, which strove for cultural independence from England whether or not they could also obtain political independence. Joyce himself had a somewhat complex relationship with Yeats, and refused to align himself with the movement. When Stephen tells Haines that he is not only a servant to the imperial British state and to the holy Roman Catholic and apostolic church, but also to "a third there is who wants me for odd jobs," he is referring to Ireland (1.303). Stephen feels the pressure of being under British rule, and is well acquainted with the crushing influence of the Catholic Church in Ireland (over 90% of Dublin would have been Catholic), but he also is wary of the dangers of insular nationalist thinking.
There are two perverse views of Irish-ness that come up in the chapter. The first is the milk woman, whom Stephen imagines as a classic Irish maid. Yet even in his imagination he can't help but think of her as barren, and the fact that she does not understand Haines when he speaks Gaelic to her further undermines the ideal image. The second is Haines's "British" view. Haines isn't all bad – he's sympathetic to the Irish, but his is the sympathy of idle curiosity. He's interested in Irish culture as if it's quaint, and responds to Stephen's seething resentment (with a dainty cigarette between his fingers) by calmly saying, "We feel in England that we have treated you rather unfairly. It seems history is to blame" (1.307). Similarly, he wants to put Stephen's line, "It is a symbol of Irish art. The cracked lookingglass of a servant," into his book of sayings, but can't imagine the pain of being Irish and feeling this to be true (1.65).
The second big thematic aspect is that of the "usurper," which invites correlations between Dedalus and Telemachus in the Odyssey, and between Dedalus and Hamlet. The Martello Tower brings to mind the court of Elsinore in Hamlet, which Haines himself observes, and the fact that Stephen insists on dressing in black after his mother's death recalls Hamlet's same insistence after the death of his father.
Martello Tower might also recall Ithaca, and Haines and Buck Mulligan slinking around the house and taking advantage of Stephen brings to mind Antinous and Eurymachos, who attempt to take over Odysseus's court while he is gone at sea. Stephen sees Buck Mulligan, in particular, as a "usurper," and he resents him. Though Stephen has broken with the Church and seeks to be a free and independent thinker, he is well aware of the constraints upon him, and is still tormented by religious and spiritual (as well as personal) questions. He can't go in for Buck Mulligan's light-hearted mockery of everything, which essentially undermines all that Stephen stands and strives for. Stephen is like Telemachus living amongst enemies that are trying to undermine him.
A fun point to end on. At one point, when Buck Mulligan is trying to buddy up to Stephen, Stephen observes that, "He fears the lancet of my art as I fear that of his" (1.68). To put this in plain English: Stephen thinks that Buck Mulligan is afraid of how he will be portrayed in Stephen's artistic work. That's interesting because Joyce based Buck Mulligan on a real-life character named Oliver St. John Gogarty. Gogarty indeed suffered from the "lancet" of Joyce's art since he was immortalized (in an unfavorable light) as Buck Mulligan.