 In Aristotle’s time, atomists held that matter was fundamentally constructed out of atoms. These atoms were indivisible and uniform, of various sizes and shapes, and capable only of change in respect of position and motion, but not intrinsic qualities. Aristotle rejected this doctrine, beginning his critique of it with a simple question: What are atoms made of? Atomists argue that they are all made of uniform matter. But why should uniform matter split into portions not themselves further divisible? What makes atoms different from macroscopic substances which are also uniform, but can be divided into smaller portions? Atomism, he argued, posits a particular size as the final point of division in completely ad hoc fashion, without giving any account of this smallest size or why atoms are this smallest size.