George Eliot was as well-read as any other female during the Victorian period. In addition to the works of Shakespeare and Scott, as well as the poetry of Byron, Coleridge, and Wordsworth, Eliot was strongly influenced by philosophical works, particularly those by Feuerbach, Spinoza, and Comte. Though raised under Evangelicalism, Eliot began to abandon those beliefs as she approached her twenties for a more humanistic perspective. The ideas she adopted from those philosophers mentioned above present themselves in her fiction, through her authorial comments. One writer (Henry James, I believe) stated that Thackeray's narrative voice is that of a social commentator while Eliot's is that of a philosopher. Each of the three philosophers that influenced Eliot added a different aspect to her belief that Christianity was greater than a religious doctrine.
Eliot translated Feuerbach's The Essence of Christianity into English in 1854. Feuerbach favored a humanistic approach to Christianity that replaced the Divine with man. Eliot embraced this idea, believing that God is a human creation fashioned to fulfill the needs of man. As a way to fulfill these needs, man must "God" to each other through love, a unifying force of humanity. While Feuerbach rejected the idea of a spiritual entity called "God," he believed that each individual was capable of giving a God-like live to his fellow man.
Similarly, Eliot was influenced by Spinoza through his work Ethics. Spinoza also believed that each individual had ingrained God-like qualities and that everyone had a moral responsibility to strengthen those qualities. Because humans are interdependent, they should recognize that their actions affect others. Consequently, Spinoza stressed tolerance and inclusiveness. Spinoza also believed in freedom, which included freedom from purpose and other constraining objectives. With freedom comes knowledge and an increase in freedom results in a happier life.
A third influence, Comte, who founded positivism, believed knowledge is derived from experience while knowledge of man comes from interaction with society. He was a realist favoring proven, scientific knowledge over idealistic, intuitive knowledge. Comte too denied the presence of a Divine influence but believed that an had a duty to be philanthropic. Essentially, each man should be what others need him to be.
Sources: George Eliot: A Biography by Gordon S. Haight
George Eliot by Elizabeth Deeds Ermarth
"The Casuitry of George Eliot" http://www.cyberpat.com/shirlsite/essays/casuist.html