Doubt is part of all religion. All the religious thinkers were doubters.

Singer’s remark frames doubt not as a failure of faith but as one of its essential engines. By insisting that “all the religious thinkers were doubters,” he distinguishes inherited, unexamined belief from reflective religion—where questioning, wrestling with God, and confronting uncertainty are integral to spiritual seriousness. The line also resonates with Jewish intellectual and devotional traditions that treat argument, interpretation, and moral inquiry as forms of engagement rather than rebellion. In this view, doubt becomes a sign of honesty and depth: the believer who thinks rigorously must face ambiguity, and the resulting tension can sharpen ethical responsibility and humility.