 The version of the Theory of Forms associated with Xenocrates is that which Aristotle ascribes to the later Plato (see Metaphysics XIII 4. 1078b10–12 for the qualification ‘later’), in which the Forms are ‘generated’ and are, in the first instance, numbers. Xenocrates operated, in parallel with Speusippus and Plato (as Aristotle reports Plato), with a scheme in which two principles--the One and something called any or all of ‘the everflowing’, ‘plurality’ (Aëtius i 3. 23), or ‘the Indefinite Dyad’ (Theophrastus, Metaphysics vi)--generate these form-numbers, and then, in turn, lines, planes, solids, and perceptible things.