In political theory and ethics the term implies a community in which the good of the whole is the mere summation of the goods of all the individuals, and in which the spring for social conduct must be found in individual initiative. It is generally opposed to socialism. Jeremy Bentham, John Stuart Mill and Herbert Spencer are its most distinguished exponents, and as a doctrine and attitude of mind it has characterized the 18th and 19th centuries in the western world. It maintained itself at first by its hostility to the outworn feudal institutions of Europe, and later by combatting an equally abstract doctrine of socialism. The theoretical inadequacy of the doctrine lies in the abstract conception of the individual, an abstractness which has been the source of both the strength and the weakness of the practical movements it has served. Like other abstractions which define more or less fixed institutions, it is waiting for a competent psychology to put a valid working content into what has been a rigid concept.