The subject matter of this thesis is a particular form of individualism - anti-collectivist individualism. To be differentiated from more collectivist, humanist strands of individualism, anti-collectivist individualism can readily be equated wi th the classic liberal creed that accompanied a new stress on the indi vidual and the emergence of a capitalist market economy in the West in the post-feudal period. The thesis places anti-collectivist individualism within the classic liberal tradition. It addresses anti-collectivist individualism both as an issue of substantive relevance to people and to politics and as an issue within sociological explanation, from the perspective of that atomism which underlies it, and through an examination of the .. :atomistic view of humankind, of history and of social causation. Specifically addressed in relation to the anti-collectivist framework are: the presumed atomistic relations of exteriority between individuals. the presumption that nothing exists in the phenomenal world other than individuals in aggregate and that explanatory power therefore rests with individuals. the presumption that to provide people with the conditions for self-reliance is a contradiction in terms. the presumption that human individuals lack the rationality to construct a 'good' society and should relinquish 'constructivist' rationalism in favour of 'evolutionary I rationalism. The question of whether capitalism and individualism are merely historically contingent (as per Abercrombie et al 1986) or are mutually defining (Friedman 1962, 1980) is also considered, it being concluded that they are not mutually defining but have entered into a second order symbiotic relation of dependence which may prove difficult to deconstruct. The ontology underlying anti-collectivist individualism is rigorously criticised, but it is suggested that individualism, far from no longer featuring in dominant discourse, as Abercrombie et al claim, remains the pivotal underlying premise of social and economic activity in the West, and indeed, being a historically evolved, even though particular manifestation of important and necessary elements of the human psyche for security, identity and self-actualisation, is likely to remain a prime mode of orientation in the West. It is claimed that this acceptance is not incompatible with communitarian and/or socialist forms of organisation.