In this essay G. Teubner considers the effects of functional differentiation in complex societies on the nature and effectiveness of contract. The author claims that contract in complex societies can no more be conceived of as the simple result of the converging will of two individuals or "parties". As a result of this, the unity of contract, i.e. its binding force, simply vanishes. The author suggests that this may result both from the empirical dynamics of functionally differentiated societies and from the theoretical deficit of systems theory The latter can provide very good observations about the inner dynamics of systems, but is blind to relationships among them. Teubner therefore argues that sociology needs to develop an alternative approach. This "new" approach should in fact be "orthogonal" to systems’ theory, in order to observe its blind spot: this means it should be focused on inter-systemic relationships.