自由主義以個人主義為其不可或缺之一環，其所謂的個人，在英美社會契約傳統內，是一種除理智與自由或自主外，別無其他屬性的人，故稱「原子人」。單從概念內涵看，原子人可指任何人，是社會契約版自由主義有普遍性的根據，也是用以說明國家之必要性，甚至道德上正當性的概念工具。一般皆以此觀念來自霍布斯與洛克兩人。實則二十世紀原子人觀念主要是科學思想的產物，霍、洛兩人非無尺寸之功，唯僅止於此。社會契約於二十世紀羅爾斯手中復興以來，陸續衍生如基本人權與政治中立、公共理性與無偏私等教義，都是單以人之理智、自由或自主為立論基礎，而無涉人實際上身分或其他特質。羅爾斯正義論也是經驗性質的理論，故其出發點之道德人格，近於經驗的原子人，而非康德之「內在人」。其個人自主性的規範寓意益受強調，不僅「自我先於目的」，且還「自我先於身分」，即以個人自主之名，忽略性別、種族、國族等生而有之之身分對自主性的限制。但忽略身分就看不出個人所處在人際與社會脈絡，致身分所形成不平等關係亦遭漠視。而原子人理論上之開放性實掩飾多數或強勢族群所思所想；社會契約淪為種族契約的一環。

Modern Liberalism consists, among others, in individualism, in which the individual refers to one who is rational, free and nothing else. It is thus dubbed as "atomic man," as it has no character whatsoever. Atomic man is often taken as coming from the theories of Social Contract, those of Hobbes and Locke in particular, though the two indeed contribute to this concept only partially. How did they contribute to the formation of it is the focus of this essay. In addition, the then prevailing thought about material substances as Galileo advocated also contributed to this "man." In this tradition it has been used to account for why the state is necessary, and even morally justified. Taken alone, atomic man can refer to every- and anyone, and is the basis on which the Social Contract liberalism is universalist, giving rise to such theories as the basic rights, political neutrality, and public reason. By the end of the twentieth century, this "man" is increasingly emphasized for its normative implicat ions, as is fabricated in the thesis of "the self prior to the ends." There is then one more dimension of it, which can be termed as "the self prior to the identities," as it inspires people to see their identities as something they should consciously determine by themselves, too. To be sure, this invites controversies, as one's identity is not entirely up to one's own will, while ignoring it results in worsening inequality by diverting people from uncovering the hidden inequalities owing to their identities in actual interpersonal relations. The putative openness of the atomic man is thus a façade, in reality stuffed by the majority dominating. Social Contract turns out to be part of racial contract.