O’Neill received a BA in sociology from the London School of Economics in 1955 where he immersed himself in classics of social and political theory from Plato to L.T.

In an autobiographical note O’Neill wrote in the early 2000s, he describes his research as being focused on Frankfurt School critical social theory and Continental phenomenology.

O’Neill’s study of the French phenomenological philosopher Maurice Merleau-Ponty led him to develop ideas on the social, productive, and political body.

[12] Inspired by the young Karl Marx’s ideas on estrangement and alienation between the worker and world, O’Neill’s Sociology as a Skin Trade in (1972) outlines his theory of how corporate capitalism operates through bodies which are transformed into objects, commodities, and machines and thus given monetary value.

[15] By focusing on the body, and combining Continental and Anglo-American intellectual traditions, O’Neill critiques conceptions of sociology that interpret and explain actions in terms of abstract categories, including functionalist and postmodern theories.

[17] In advancing a conception of what he calls 'Orphic Marxism', and through a reading of Herbert Marcuse and Michel Foucault, he argues that this ‘reformulation of Marxist humanism gives emphasis to its civility over its industrialism’.

[19] By centring critical intelligence on the body, and by bridging emancipatory, analytical, and expressive ways of knowing, O’Neill examines how social alienation and inequality can be viewed as more or less a common experience.

[22] In the essays collected in Critical Conventions (1992) and Incorporating Cultural Theory (2002), which discuss such thinkers as Roland Barthes and Jacques Derrida along with the fiction of Italo Svevo and James Joyce, among others, he broadens this approach to post-structuralist interpretation into a meta-psychoanalytic theory of what he calls 'homotextuality/gynesis' through a series of critical studies of the conventions of style and disciplinarity in the literary and social sciences.

[27] Without ignoring the lessons of Marxist theory and in part by displacing Eurocentric thought through critiques of the work of Talcott Parsons, Hannah Arendt, John Rawls, and Gilles Deleuze and Félix Guattari, these later writings address urgent issues of childhood and family in the context of liberal-communitarianism by formulating a concept of what he calls ‘civic capitalism’.