The meaning of reciprocity and fairness within contracts seems to be a constant source of disagreement and a continuous subject of ongoing theoretical debates in legal and moral philosophy. It is especially discernible within a mainstream of the classical post-Aristotelian tradition. The problem seems to pertain to the interdependence between the two parties of contract and their respective obligations. Mutual interdependence of contractual or pre-contractual obligations is usually indentified with a Greek term συνάλλαγμα, playing a significant role in Aristotelian philosophy, especially in theory of justice. Such interdependence has so far been analysed within a context of Pythagorean mathematics and has eventually been modelled in game theory. Game theoretic models such as Nash solution to bargaining problem are based on the assumption that contract consist in strategic interaction between agents. The paper explores the interactions between Aristotelian theory of commutative justice and contemporary advances in game theory and philosophy of contracts, aiming at addressing the question whether the Aristotelian concept of synallagma could still be regarded as a central category of contract law.