Who Are You Going to Believe, the Philosopher or Your Own Eyes?

Surely, [Bertrand] Russell could scarcely have denied that the world which he believed in as a philosopher [i.e., a world of sense-data rather than material objects] was hardly the world which he lived in as a human being. Thus imagine Russell shaking hands with a friend, or haranguing a mass meeting in condemnation of the U.S. military involvement in Vietnam. Doubtless in such circumstances he might have stuck to his philosophical conviction that any statements he might make concerning the people and things in the immediate situation confronting him were reducible by definitions-in-use to statements only about sense data and not about people and things at all. Yet no less doubtless would it appear that even Russell could hardly have been so committed to his own philosophy as to assume in his attitudes and behavior, even if not in his thoughts, that the people and things that he was having to do with were but so many groupings and series of sense data.

--Henry B. Veatch, Aristotle: A Contemporary Appreciation