John Witherspoon (February 5, 1722 - November 15, 1794) was a Scottish-American Presbyterian minister and a Founding Father of the United States. Witherspoon embraced the concepts of Scottish Common Sense Realism, and while president of the College of New Jersey (1768-1794; now Princeton University), became an influential figure in the development of the United States' national character. Politically active, Witherspoon was a delegate from New Jersey to the Second Continental Congress and a signatory to the July 4, 1776, Declaration of Independence. He was the only active clergyman and the only college president to sign the Declaration.

According to Herbert Hovenkamp, Witherspoon's most lasting contribution was the initiation of the Scottish Common-Sense Realism, which he had learned by reading Thomas Reid and two of his expounders Dugald Stewart and James Beattie. Witherspoon revised the moral philosophy curriculum, strengthened the college's commitment to natural philosophy, and positioned Princeton in the larger transatlantic world of the republic of letters. Although he was a proponent of Christian values, Witherspoon's common sense approach to the public morality of civil magistrates was more influenced by the Enlightenment ethics of Scottish philosophers Francis Hutcheson and Thomas Reid than the Christian idealism of Jonathan Edwards. In regard to civil magistrates, Witherspoon thus believed moral judgment should be pursued as a science. He held to old concepts from the Roman Republic of virtuous leadership by civil magistrates, but he also regularly recommended that his students read such modern philosophers as Machiavelli, Montesquieu, and David Hume, even though he disapproved of Hume's "infidel" stance on religion. Virtue, he argued, could be deduced through the development of the moral sense, an ethical compass instilled by God in all human beings and developed through religious education (Reid) or civil sociability (Hutcheson). Witherspoon saw morality as having two distinct components: spiritual and temporal. Civil government owed more to the latter than the former in Witherspoon's Presbyterian doctrine. Thus, public morality owed more to the natural moral laws of the Enlightenment than to revealed Christianity. In his lectures on moral philosophy at Princeton, required of all juniors and seniors, Witherspoon argued for the revolutionary right of resistance and recommended checks and balances within government. He made a profound impression on his student James Madison, whose suggestions for the United States Constitution followed both Witherspoon's and Hume's ideas. The historian Douglass Adair writes, "The syllabus of Witherspoon's lectures . . . explains the conversion of the young Virginian to the philosophy of the Enlightenment." Witherspoon accepted the impossibility of maintaining public morality or virtue in the citizenry without an effective religion. In this sense, the temporal principles of morality required a religious component which derived its authority from the spiritual. Therefore, public religion was a vital necessity in maintaining the public morals. However, in this framework, non-Christian societies could have virtue, which, by his definition, could be found in natural law. Witherspoon, in accordance with the Scottish moral sense philosophy, taught that all human beings, Christian or otherwise, could be virtuous, but he was nonetheless committed to Christianity as the only route to personal salvation.

was he religious?
Thomas Reid than the Christian idealism of Jonathan Edwards.