Overlapping consensus is a term coined by John Rawls in Theory of Justice and developed in Political Liberalism.
The term refers to how supporters of different comprehensive doctrines can agree on a specific form of political organization. These doctrines can include religion, political ideology or morals. However, Rawls is clear that such political agreement is narrow and focused on justice. This consensus is reached, in part, by avoiding the deepest arguments in religion and philosophy.
The overlapping consensus “depends, in effect, on there being a morally significant core of commitments common to the ‘reasonable’ fragment of each of the main comprehensive doctrines in the community” (D'Agostino 2003).
The commitments as applied to a liberal society, for example, would be basic human rights and freedoms such as that of expression and religion, as well as abiding by notions of democracy and the rule of law.
See also 
- D'Agostino, Fred, "Original Position", The Stanford Encyclopedia of Philosophy (Summer 2003 Edition), Edward N. Zalta (ed.).
- Rawls, John. "The Idea of an Overlapping Consensus." Oxford Journal of Legal Studies, Vol. 7, No. 1, (Spring, 1987), pp. 1-25.