 But that any whichever of these is a true cause can easily be proven indeed in the case of material, formal, and efficient [causes], for any whatever of these manifestly inflows some being… But concerning the final cause there can be some reason for doubting, since no real being is presupposed in it by which it could cause (De fine vero potest esse nonnulla dubitandi ratio, quia nullum esse reale in eo praesupponitur, quo causare possit: DM XIII 3.3)