As an empiricist , Russell assumed that all human knowledge must begin with sensory experience . Thus, the contents of sensory experience are both public and objective. From this beginning, according to Russell, all else follows by logical analysis. What we ordinarily call physical objects are definite descriptions constructed logically out of just such epistemic atoms. Careful application of this principle, together with the techniques of logical analysis, accounts for everything we can know either by acquaintance or by description .
Some cases do call for special treatment.
Suitably analyzed, however, all of human knowledge can be seen to rest solely upon the collective content of human experience. Abstract philosophical matters were not all that Russell cared about. At the height of his career, Russell spent years in jail as a conscientious objector to British involvement in the First World War, and this vocal pacifism resulted in the termination of his professorship at Cambridge. Although he came to regard the threat of Fascism as great enough to warrant the Second World War, Russell was profoundly concerned about the invention of atomic weapons with the capacity to destroy human civilization on an unprecedented scale. Russell's efforts to secure an academic career in the United States were thwarted by conservative opponents who drew attention to his unconventional opinions regarding sexual morality and organized religion.