The Book of Kells is not only a leitmotif in James Joyce`s Finnegans Wake,but also a thematic and an aesthetic source of it. The two hens painted in the Book of Kells inspire both the hen described in Finnegans Wake as well as the idea of hidden truth which leads to the difficult style of Finnegans Wake. The connection between these two books indicates the connection between HCE and Jesus Christ. Furthermore, the richness and variation of Finnegans Wake could better be understood with the rich and varied decorations in the Book of Kells, which shows an aesthetic difference from that of high modernism.