Max Weber's classical conceptualization of instrumental rationality (formal, practical, scientifically theoretical) is interpreted by its associated social relations and its neurocognitive infrastructure. Such rationality requires calculation, planning, and their interaction. Calculation is linked to a larger cognitive structure, left-hemisphere-dependent logical–analytic cognition, which includes propositional logic, deductive reasoning, linear and numeral thinking, linear time consciousness, and the quantitative assessment of value. Planning is linked to the central-executive functioning of the frontal lobes and associated brain structures. The language-based integration of calculation and planning is interpreted on both sociological and neurobiological levels, the result being a neurosociological level of analysis of instrumental rationality.