  Explaining complex properties by reducing them to more elementary ones was not an enterprise unique to the mechanical philosophers. After all, it was a central Aristotelian thesis that the behaviour of materials was due to the proportions of the four elements in them, whilst the elements themselves owed their properties to the interaction of the hot and the cold and the wet and the dry, the fundamental active principles in nature. What a mechanical atomist like Boyle needed, and attempted, to do was establish that they could provide examples of successful mechanical reductions that were clear and intelligible. It was to this end that Boyle stressed how the workings of a key could be explained in terms of nothing other than its shape and size relative to the lock and the workings of a clock can be explained by appeal to nothing other than the properties of its parts.