This essay is a critique of rationalist approaches in religions, their sects and heresies.

David Miller elegantly and provocatively reformulates critical rationalism—the revolutionary approach to epistemology advocated by Karl Popper—by answering its most important critics. He argues for an approach to rationality freed from the debilitating authoritarian dependence on reasons and justification. "Miller presents a particularly useful and stimulating account of critical rationalism. His work is both interesting and controversial . . . of interest to anyone with concerns in epistemology or the philosophy of science." —Canadian Philosophical Reviews

Reprint of the original, first published in 1865. Ninth Edition Revised.