The presumption of rationalism is that one always should use reason in the acquisition of knowledge rather than faith. Reason can move mountains whilst faith makes for mountains of castles in the air.
Reason does not bring mad scientists or despotism; those are faith-based activities as not based in reason and real fact but instead in whims and disregard of facts. Reason is not without emotions.
Faith is the we just say so of credulity.. It begs the question of its subject [Articulett@ Skeptic Society]. Science is acquired knowledge whilst faith , as Sydney Hook remarks, begs the question of being knowledge.
Contrary to advance theologian haughty John Haught, Clifford Richard Dawkins does not make here an idiosyncratic definition of faith, nor do I, but use the word ad one does in stating that one must have faith.And it is no false dilemma to claim thus that reason and faith do in fact conflict rather than faith complements reason.
William Kingdon Clifford rightly maintains that we should never accept a claim without sufficient evidence; advance theologian Keith Ward maintains that with that heuristic method and attitude, we could never get out of bed!Nay, the amount varies, much of life's daily activities require no further evidence finding. He sets up the straw man of the all or nothing fallacy.
Advanced theologians abdicate reason like the primitive ones like Pat Robertson or Norman Geisler; faith does that to people!