This book considers how certainty and faith are related in the Christian faith. It asks: How certain can Christian believers be about their beliefs about God? Should Christians doubt the assurance of their salvation? The chapters provide a historical analysis of both certainty of faith and assurance from the early Church to modern times while also paying attention to confessional differences. The author explores contemporary debates in analytic epistemology on the certainty and fallibility of our beliefs and argues for a fallibilist understanding of Christian faith. The book also addresses some less-discussed arguments that threaten the certainty of faith and offers an account of faith as cognitive practice. It will be of interest to scholars of both theology and philosophy.