Why did medieval prose romances often lack a single central theme?

Medieval prose romances often lacked a single central theme because of a specific structural technique known as interweaving. Rather than adhering to the Aristotelian principle of organic unity—which requires a work to be an indivisible, isolated whole—these romances were designed to absorb and connect a vast array of independent themes, episodes, and characters.1

This structure allowed narratives to diverge, subdivide, join, and separate, creating an interlocking whole that functioned as a cohesive, impregnable structure without needing a single center. For example, cycles like the Lancelot-Grail could simultaneously incorporate disparate elements such as the story of Lancelot, the rise and fall of Arthur’s kingdom, and the Quest of the Grail.1

This capacity for expansion meant that prose romances could grow through continuations or by absorbing new material, such as the stories of Tristan and Iseult or even legends involving figures like Alexander the Great. Consequently, internal cohesion in these works was achieved not through a singular thematic focus, but through the constant seeking of connections with other compositions and the elaboration of previously underdeveloped themes.1