Purpose -The concept of contract contributes extensively to an essentialist conception of the organization (the contract would then be its essence), a descriptive method (describing the organization as a contract or set of contracts), and a normative standpoint. More recently, it has been epitomized by the "psychological contract". The concept of contract is about will, agreement, obligation, promise, commitment, staying true to one's commitments, cooperation, sanction and bond. The purpose of this paper is to discuss these manifestations prior to comparing the notion of social contract with psychological contract based on two criteria: an anthropology of the individual and an anthropology of the contract. Design/methodology/approach -After delineating the notion of contract (and its correlates agency, gift, exchange and association) and reviewing the "epithet-based" contracts, the two dimensions of the contract (social and psychological) will be addressed and compared based on two anthropologies, one of the individual and one of the contract. Findings -This comparison underscores the relevance of contractualism today and the richness of comparing across different eras and perimeters. If these two aspects have anything in common, it is whatever links the contract with sociality. Research limitations/implications -This comparing process must underscore two limitations, namely anachronism (the two texts were written two centuries apart), and underpinning, a political underpinning in the social contract and an organizational underpinning in the psychological contract. It thus looks as though the organization was made of the same substance as the nation, which -like the notion of governance -may lead to some kind of confusion between contract and constitution, contracting power and constituent powers. Practical implications -The paper discusses a key notion in political philosophy and organization science. Originality/value -The paper presents a comparison between two key conceptions of the notion of contract.