Hugo's religious views changed radically over the course of his life. In his youth, he identified himself as a Catholic and professed respect for Church hierarchy and authority. From there he became a non-practicing Catholic, and increasingly expressed anti-Catholic and anti-clerical views. He frequented Spiritism during his exile (where he participated also in many séances conducted by Madame Delphine de Girardin), [6] [7] and in later years settled into a Rationalist Deism similar to that espoused by Voltaire. A census-taker asked Hugo in 1872 if he was a Catholic, and he replied, "No. A Freethinker".

After that point, Hugo never lost his antipathy towards the Catholic Church, due largely to what he saw as the Church's indifference to the plight of the working class under the oppression of the monarchy; and perhaps also due to the frequency with which Hugo's work appeared on the Church's Index Librorum Prohibitorum (Hugo counted 740 attacks on Les Misérables in the Catholic press). On the deaths of his sons Charles and François-Victor, he insisted that they be buried without a crucifix or priest, and in his will made the same stipulation about his own death and funeral. However, although Hugo believed Catholic dogma to be outdated and dying, he never directly attacked the actual doctrines of the Church.

Hugo's Rationalism can be found in poems such as Torquemada (1869, about religious fanaticism), The Pope (1878, anti-clerical), Religions and Religion (1880, denying the usefulness of churches) and, published posthumously, The End of Satan and God (1886 and 1891 respectively, in which he represents Christianity as a griffin and Rationalism as an angel). "Religions pass away, but God remains", Vincent van Gogh wrote that Hugo declared (but actually it was Jules Michelet). Christianity would eventually disappear, he predicted, but people would still believe in "God, Soul, and the Power".