Their bond began in the early 1920s when they met as students at the École Normale Supérieure in Paris, one of the most prestigious universities of the city. They formed a profound intellectual and emotional connection, sharing a commitment to existentialist philosophy and a rejection of societal norms, including the conventions of monogamous relationships. Despite their deep affection for each other, Sartre and de Beauvoir agreed on an open relationship, characterized by personal freedom and a rejection of possessiveness. They pledged lifelong partnership, but with the understanding that they were free to engage in other romantic and sexual relationships.

Here is an excerpt from their correspondence in 1948:

"My sweet little one, my dear little soul, You wrote me such a sweet little letter that touched my heart because I know it's true—no, you are not a whitewashed tomb, my heart, and I felt it so strongly again in Ramatuelle. I also know that I will never lose you, that no matter what happens, you will always be my dear little ally, my other self. And I am not a tomb either; my heart was beating fast, and my hands were trembling just now at the post office when I looked for and opened your letter."

Their partnership endured for more than 50 years, marked by intellectual collaboration, emotional support, and a commitment to each other's personal and professional growth. Despite their unconventional arrangement, they remained emotionally connected and deeply involved in each other's lives until Sartre's death in 1980 and de Beauvoir's passing in 1986. Their relationship, marked by intellectual intensity, mutual respect, and unconventional choices, continues to fascinate and inspire discussions about love, freedom, and the complexities of human relationships. They challenged societal norms, paving the way for alternative models of partnerships.