Deleuze opens Difference and Repetition with the claim that ‘Repetition is not generality’ (DR 1/1). The incommensurability of generality, and the related concept of law, is the central theme of the introduction, and of much of the book itself. We normally see laws as applying to all particular entities that resemble one another in a pertinent way, that is, all particulars that fall under a generality. So, for instance, the laws of gravitation apply to particular bodies in so far as they have mass, Bernoulli's principle applies to all uncompressible fl uids moving at low speeds. Likewise, for Kant, universal moral laws govern the behaviour of all beings who share the property of rationality. In all of these cases, it seems to be the case that repetition plays a central role in the formulation of laws. Scientifi c laws are formulated by repeated experimentation, and Kant's moral law appears, in the form of the categorical imperative, to provide a test of what actions can be repeated. Deleuze discusses three different ways of relating to the world in which we might think that we encounter repetition: scientifi c experiment, moral law and the psychology of habit. Deleuze's general strategy in these opening sections is to show that there is a problem with our notion of the law in natural sciences, and then to show how other conceptions of the law are ultimately founded on this one case. His argument is that in the case of scientifi c experiment, we do not really encounter repetition. In the case of moral law and the psychology of habit, while these do appear to offer us a true understanding of repetition, they do so only on the basis of drawing analogies with scientifi c repetition, so ultimately do not get beyond the limitations of this model.