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Spiritual life

Analysing her deeds and achievements, Pope John Paul II said: "Where did Mother Teresa find the strength and perseverance to place herself completely at the service of others? She found it in prayer and in the silent contemplation of Jesus Christ, his Holy Face, his Sacred Heart." Privately, Mother Teresa experienced doubts and struggle in her religious beliefs which lasted nearly 50 years, until the end of her life. Mother Teresa expressed grave doubts about God's existence and pain over her lack of faith:

Where is my faith? Even deep down there is nothing but emptiness and darkness. If there be God – please forgive me. When I try to raise my thoughts to Heaven, there is such convicting emptiness that those very thoughts return like sharp knives and hurt my very soul.

Other saints (including Teresa's namesake Thérèse of Lisieux, who called it a "night of nothingness") had similar experiences of spiritual dryness. According to James Langford, these doubts were typical and would not be an impediment to canonisation.

After ten years of doubt, Mother Teresa described a brief period of renewed faith. After Pope Pius XII 's death in 1958, she was praying for him at a requiem mass when she was relieved of "the long darkness: that strange suffering." However, five weeks later her spiritual dryness returned.

Mother Teresa wrote many letters to her confessors and superiors over a 66-year period, most notably to Calcutta Archbishop Ferdinand Perier and Jesuit priest Celeste van Exem (her spiritual advisor since the formation of the Missionaries of Charity). She requested that her letters be destroyed, concerned that "people will think more of me – less of Jesus."

However, the correspondence was compiled in Mother Teresa: Come Be My Light. Mother Teresa wrote to spiritual confidant Michael van der Peet, "Jesus has a very special love for you. as for me, the silence and the emptiness is so great, that I look and do not see – listen and do not hear – the tongue moves but does not speak. I want you to pray for me – that I let Him have free hand."

In Deus caritas est (his first encyclical), Pope Benedict XVI mentioned Mother Teresa three times and used her life to clarify one of the encyclical's main points: "In the example of Blessed Teresa of Calcutta we have a clear illustration of the fact that time devoted to God in prayer not only does not detract from effective and loving service to our neighbour but is in fact the inexhaustible source of that service." She wrote, "It is only by mental prayer and spiritual reading that we can cultivate the gift of prayer."

Although her order was not connected with the Franciscan orders, Mother Teresa admired Francis of Assisi and was influenced by Franciscan spirituality. The Sisters of Charity recite the prayer of Saint Francis every morning at Mass during the thanksgiving after Communion, and their emphasis on ministry and many of their vows are similar. Francis emphasised poverty, chastity, obedience and submission to Christ. He devoted much of his life to serving the poor, particularly lepers.