The opening lines of the Meteorology suggest that Aristotle was centrally concerned with the integration of a range of different natural investigations into a single explanatory project. I will try to illustrate how this integration is achieved by looking at the place of the De motu animalium (De motu) in Aristotle’s philosophy of nature. At least at first sight, this short but difficult treatise does not seem to be a very promising case. It has been argued that the De motu does not belong to natural philosophy (or to any other Aristotelian science for that matter). On this interpretation, the De motu would be an interdisciplinary work or even a [deliberate and fruitful] departure from the Organon model (Nussbaum 1978: 113). Hopefully, a fresh look at the De motu will help, not only to establish that it pertains to natural philosophy, but also to show how it contributes to the explanatory project pursued by Aristotle.