Philosophy has as its task not only the discovery of the determinations into which all things fall, but also the explanation of how these determinations arise. In Proclus we may distinguish three related sorts of deter- minations. First, there are the determinations which emerge within any given taxis in the hierarchy of all things and which may be thought of as its content, such as the intelligible genera in Intellect (Nous), or the various animal species in the material world.1 Second are the deter- minations which give a particular taxis its overall character, such as the simplicity of the henads, or the temporality of souls. Finally, there are the determinations which emerge through discursive thinking itself, the logoi through which we grasp the determinations of all things. What fol- lows is an account of the character and origin of these related sorts of determination in Proclus’ system.