ABSTRACT. Critical Psychology is discussed as an historical science of the sub- ject. The confrontation of human and machine is used to differentiate subjects in action from notions of isolated, formal mental mechanisms. An investiga- tion of operators’ regulation in a control room reveals issues of how subjects must re-arrange conditions to act more appropriately. The operators do not know everything necessary to act. This means that they must act on the basis of a concrete, varied, and situated understanding of their work. Since the dilemmas of work have no correct solutions, the operators must break rules to follow them and thereby re-arrange conditions. Each worker has his perspec- tive on the problems. The differences are sorted out in conflictual cooperation. This challenges the more mediated aspects of work conditions.