Political rationality and calculation | Tangente

This is how Paul Valéry, in his Regards sur le monde actuel (1945), depicted the sense of vertigo that can arise when an important political decision must be made. In truth, this applies no less to any other field: the question "What should we do?" almost immediately entails its corollary, "How can we know what to do?" Mathematics has often been called upon to answer this second question with a view to answering the first. Today, public-policy evaluation provides a practical example, just as the notion of rational consumer behavior provides a theoretical one.

In political theory too, calculation is steadily gaining ground as a tool for understanding human rationality. This has created difficulties—and even problems.

Action as an equation -------------------------------

Historically, the first attempt to put the rationality of human action on a mathematical footing dates back to the work of the young Gottfried Wilhelm Leibniz (1646–1716), who at the age of 20 published his doctoral thesis, entitled Dissertatio de arte combinatoria. In it, he set out to create a universal language, the characteristica universalis, a kind of generalized mathematical notation capable of expressing scientific and philosophical concepts, as well as concepts drawn from everyday life. To this end, he envisaged a calculating machine capable of addition, subtraction, multiplication and division, which he hoped could gradually be made complex enough to solve not only arithmetic operations but all manner of questions: "There will no longer be any need for two philosophers to debate at greater length than two mathematicians, since they need only take up their pens, sit down at their calculating table (calling upon a friend if they wish), and say to one another: "Let us calculate." "