 The reason Russell believes many ordinarily accepted statements are open to doubt is that they appear to refer to entities that may be known only through inference. Thus, underlying Russell’s various projects was not only his use of logical analysis, but also his long-standing aim of discovering whether, and to what extent, knowledge is possible. “There is one great question,” he writes in 1911. “Can human beings know anything, and if so, what and how? This question is really the most essentially philosophical of all questions” (quoted in Slater 1994, 67).