In April 1970, Grisey read Gravity and Grace (1947), by the legendary theologian and philosopher Simone Weil. It was auspicious reading for the young composer: Weil, a devout Catholic from a Jewish background, was a profound religious thinker who also “had a deep veneration for the great Hindu and Taoist writings,” as her editor Gustav Thibon writes. In additional to her ecumenicalism, Weil held a near-religious veneration for art. For her, as for Grisey, faith and musical listening were close to the same thing. Weil writes:

In other ways too, Weil's work dovetailed neatly with Grisey's instinct toward a less dogmatic, more mystical and sensual version of his Catholic faith. Gravity and Grace, written in aphoristic style, contains many ideas that Grisey integrated into his aesthetic, especially the equivalence between “extreme attention” and prayer and the insight that “Time does us violence; it is the only violence.” (The second idea resurfaces much later, in Grisey's Quatre chants pour franchir le seuil.) Weil had a carnal understanding of Christianity that aligned with Grisey's own: in Waiting for God, she writes, “God has provided that when his grace penetrates to the very center of a man and from there illuminates all his being, he is able to walk on the water without violating any of the laws of nature.”

Grisey wrote far fewer diary entries in the 1970s, making it impossible to trace his month-by-month development as in the previous decade. But the ones that do exist contain important aesthetic reflections. Reading Weil, Grisey emphasized the humanist distinction that Christ had not suffered for God but suffered for mankind on behalf of God. Returning to a theme of his youth, he also noted Weil's injunction to “be only an intermediary between the uncultivated ground and the ploughed field, between the data of a problem and the solution, between the blank page and the poem, between the starving beggar and the beggar who has been fed.”