In a 1908 letter to Victoria Welby, Peirce defined a ‘true man of science’ as ‘belonging to a social group all the members of which sacrifice all the ordinary motives of life to their desire to make their beliefs concerning one subject conform to verified judgments of perception together with sound reasoning’ (SS 75). As Peirce goes on to explain, acting in this way shows that the scientist implicitly believes in a universe ‘governed by reason,’ i.e. one guided by principles which can be discovered and understood. If her reasoning is really sound, she will be aware that all of her beliefs (and those of her social group) are fallible. Yet in order to carry out her role of questioning, her investigative practice must be governed by those implicit beliefs which are not currently subject to doubt. The pure scientist is the one who devotes himself “religiously” to the quest for truth.