From a very young age Levertov was influenced by her religion, and when she began writing it was a major theme in her poetry. Through her father she was exposed to both Judaism and Christianity. Levertov always believed that her culture and her family roots had inherent value to herself and her writing. Furthermore, she believed that she and her sister had a destiny pertaining to this. When Levertov moved to the United States, she fell under the influence of the Black Mountain Poets, especially the mysticism of Charles Olson. She drew on the experimentation of Ezra Pound and the style of William Carlos Williams, but was also exposed to the Transcendentalism of Thoreau and Emerson. Although all these factors shaped her poetry, her conversion to Christianity in 1984 was the main influence on her religious writing. Sometime shortly after her move to Seattle in 1989, she became a Roman Catholic. In 1997, she brought together 38 poems from seven of her earlier volumes in The Stream & the Sapphire, a collection intended, as Levertov explains in the foreword to the collection, to "trace my slow movement from agnosticism to Christian faith, a movement incorporating much doubt and questioning as well as affirmation."
Denise Levertov wrote many poems with religious themes throughout her career. These poems range from religious imagery to implied metaphors of religion. One particular theme was developed progressively throughout her poetry. This was the pilgrimage/spiritual journey of Levertov towards the deep spiritual understanding and truth in her last poems.
One of her earlier poems is "A Tree Telling of Orpheus", from her book Relearning the Alphabet. This poem uses the metaphor of a tree, which changes and grows when it hears the music of Orpheus. This is a metaphor of spiritual growth. The growth of the tree is like the growth of faith, and as the tree goes through life we also go through life on a spiritual journey. Much of Levertov's religious poetry was concerned with respect for nature and life. Also among her themes were nothingness and absence.
In her earlier poems something is always lacking, searching, and empty. In "Work that Enfaiths" Levertov begins to confront this "ample doubt" and her lack of "burning surety" in her faith. The religious aspect of this is the doubt vs. light debate. Levertov cannot find a balance between faith and darkness. She goes back and forth between the glory of God and nature, but doubt constantly plagues her.
In her earlier religious poems Levertov searches for meaning in life. She explores God as he relates to nothing(ness) and everything. In her later poetry, a shift can be seen. "A Door in the Hive" and "Evening Train" are full of poems using images of cliffs, edges, and borders to push for change in life. Once again, Levertov packs her poetry with metaphors. She explores the idea that there can be peace in death. She also begins to suggest that nothing is a part of God. "Nothingness" and darkness are no longer just reasons to doubt and agonise over. “St. Thomas Didymus” and “Mass” show this growth, as they are poems that lack her former nagging wonder and worry.
In Evening Train, Levertov’s poetry is highly religious. She writes about experiencing God. These poems are breakthrough poems for her. She writes about a mountain, which becomes a metaphor for life and God. When clouds cover a mountain, it is still huge and massive and in existence. God is the same, she says. Even when He is clouded, we know He is there. Her poems tend to shift away from constantly questioning religion to accepting it simply. In “The Tide”, the final section of Evening Train, Levertov writes about accepting faith and that not knowing answers is tolerable. This acceptance of the paradoxes of faith marks the end of her "spiritual journey".
Levertov’s heavy religious writing began at her conversion to Christianity in 1984. She wrote a great deal of metaphysical poetry to express her religious views, and began to use Christianity to link culture and community together. In her poem “Mass” she writes about how the Creator is defined by His creation. She writes a lot about nature and individuals. In the works of her last phase, Levertov sees Christianity as a bridge between individuals and society, and explores how a hostile social environment can be changed by Christian values.