Love
There is no more prevalent theme in Marie's lays than love. Her stories consider various perspectives on love relationships, including marriage, extramarital affairs, love between lords and vassals, and love between parents and children. Each lay considers how different types of love either bring happiness, as in "Guigemar," or how they lead to unhappiness, as in "Equitan." Sometimes a sacred, happy love is quashed by the world outside it, as in "Laustic," whereas other times selfish loves are punished, as in "Bisclavret." Every single one of the poems can be understood in terms of this theme.
Loyalty
Like the theme of love, the theme of loyalty helps to elucidate Marie's perspectives on the different scenarios she presents. Lapses in loyalty provide the central thrust on occasion – like in "Equitan" or Bisclavret – but the idea that lords can show a lack of loyalty to their vassals is sprinkled throughout. Consider Arthur's lack of loyalty to Lanval, or the way Eliduc's lord causes him to leave his home because the lord believes slander. "Eliduc" is particularly based on loyalty, since that theme provides insight into the central conflict of the main character.
Possessiveness
Possessiveness, especially that of fathers towards their daughters or old men towards their wives, creates many unhappy situations in the lays. The fact that it is typically beautiful young women who are controlled by patriarchal guardians provides some insight into Marie's perspective as a woman, and it also helps to understand why these women are so attracted to men who bring the potential of rescue. The lays that exhibit possessive fathers are "Guigemar," "Les Deus Amanz," "Yonec," "Laustic," "Milun," and to a lesser extent "Eliduc."
Fate
Marie's sense of fate is quite unique, especially in terms of love. Marie never attempts to claim that people can control falling in love, and her language frequently stresses how love strikes in spite of our desires. She tends to speak of it as a force that is like fate. However, Marie's consistent point is that humans are to be judged not by the forces that affect our feelings, but instead how we act in response to those emotions. The people who are to be respected are those who can control themselves, like Tristam or Eliduc, whereas those who give in to their feelings, like Equitan, are to be judged harshly.
Charity/Selflessness
Perhaps what Marie prizes as virtuous above all else is love based in selflessness and charity. The end of her final lay – "Eliduc" – is the best indication of this theme, since all of the lovers involved eschew their romantic entanglements for a life devoted to charity and God. However, the most virtuous characters throughout are those who love selflessly, without thinking too much of themselves. Le Fresne is perhaps the second best example, though there are plenty other examples, such as Lanval.
Chivalry
Marie's greatest literary accomplishment in the Lais is the way she celebrates the chivalrous court culture of her day while subtly and consistently lambasting it. The search for fame and self-glorification works in direct contrast to the charity and selflessness that Marie prizes as the most virtuous of loves. The pursuit of celebrity and women works against people who otherwise love one another (like in "Milun"), and makes it hard to remain selfless.
Storytelling
Throughout her stories, Marie makes explicit her role as storyteller, sometimes through authorial interjections and sometimes through self-praise. In terms of the former, Marie often interrupts her story either to directly suggest the theme of a particular lay, or sometimes to consider the details of the story, saying something like "I think" about a particular fact. The effect of this is potentially to suggest the truth of the stories (since it suggests she is merely remembering a true story, rather than making it up) and potentially just to exhibit playfulness. Marie also praises herself as a storyteller, beginning with her "Prologue," which could have a historical relevance (to defend herself against detractors) or could be meant to stress that storytelling is more than just entertainment – it is a vehicle for communicating profound truths.
