Aristotle thinks that the term ‘cause’ can be used in three different ways. ‘The first cause,’ he says, ‘is matter – without it nothing can be brought into existence. The second is the craftsman, and the third is form, which is impressed on every single piece of work as on a statue.’ This last is what Aristotle calls the idos. ‘And,’ he says, ‘there is a fourth as well, the purpose of the whole work.’
