Spinoza’s law : the epicurean definition of the law in the Theological Political Treatise

In the first few pages of chapter 4 of his Theological Political Treatise (1670), Spinoza defines his conception of the law.1 In fact, he defines the law twice, first in terms of compulsion or necessity and then in terms of use. I would like to investigate here these definitions, in particular the second one, as it is Spinoza’s preferred one. The difficulty with understanding this definition is that it contains an expression, ratio vivendi, that is repeated several times in the first few pages of chapter 4, but, unless it is taken as a technical term referring to law as use, it is easy to mistake it as a casual expression that might mean different things each time. As a result, it is indispensable to turn to the Latin text to unlock the technical meaning of ratio vivendi.