Throughout his life his dissent had scorned easy popularity with either the right or the left. Untamable, he had profound trust in the ultimate power of rationality, which he voiced with an undogmatic but quenchless zeal. Philosophically and ethically Russell's thought grew in reaction against the extremes he encountered. He answered the idealism of F. H. Bradley and J. M. E. McTaggart with a logical atomism founded on a rigorous empirical base: he was deeply convinced of the logical independence of individual facts and the dependence of knowledge on the data of original experience. His emphasis on logical analysis influenced the course of British philosophy in the 20th cent.
One of his most important notions was that of the logical construct, the realization that an object normally thought of as a unity was actually constructed from various, discrete, simpler empirical observations. The technique of logical constructionism was first employed in his mathematical theory. Under the influence of the symbolic logic of Giuseppe Peano, Russell tried to show that mathematics could be explained by the rules of formal logic. His demonstration involved showing that mathematical entities could be "constructed" from the less problematic entities of logic. Later he applied the technique to concepts such as physical objects and the mind.
Although he came to have misgivings about logical atomism and never assented to all the propositions of empiricism, he never ceased trying to base his thought—mathematical, philosophical, or ethical—not on vague principle but on actual experience. This can be seen in his pacifism as well as in his philosophy: he objected to specific wars in specific circumstances. So, in the circumstances preceding World War II he could abandon pacifism and, following the war, resume it.
Similarly, in ethics he described himself as a relativist. Good and evil he saw to be resolvable in (or constructed from) individual desires. He did distinguish, however, between what he called "personal" and "impersonal" desires, those founded mainly on self-interest and those formed regardless of self-interest. He admitted difficulties with this ethical stance, as well as with his logical atomism. As much as anything, his thought was characterized by a pervasive skepticism, toward his own thought as well as that of others.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.