The idea of toleration is inextricably connected with the history of liberalism. Arguably liberal political theory's first direct encounter with the conceptual problems posed by legal discrimination and unequal treatment of minorities emerged from the religious controversies of the early modern period. It is in this context that John Locke emerges as an important but controversial figure in the history of political thought. On the one hand, it is widely acknowledged that it is with Locke that the argument for religious toleration made one of its first, and still most celebrated, appearances. On the other hand, some scholars question whether Locke's notion of toleration was too narrow and limited, and too dependent on seventeenth-century theological assumptions to have any real purchase in diverse modern liberal societies today.

For instance, Jonathan Israel in his important recent works on Enlightenment Philosophy highlights Locke's toleration theory as prime evidence for relegating him to the status of an “essentially conservative” thinker who played little or no role in the revolution in philosophy led by Spinoza, which produced the modern world we know. For Israel, the chief defects in Locke's account of toleration were his notorious exceptions to toleration, most notably atheists and Roman Catholics, as well as what Israel takes to be the fundamentally theological orientation of Locke's argument for toleration and his larger worldview.