METAPHYSICS subject matter But metaphysics, and only metaphysics, demonstrates the existence of God So God cannot be the subject matter of metaphysics (Metaph 5–6) Being, the object of metaphysics, is something whose existence does not have to be proved Metaphysics studies being as such, not particular types of being, such as material objects It studies items in the Aristotelian categories, which are as it were species of being It treats of topics such as the one and the many, potentiality and actuality, universal and particular, the possible and the necessary—topics that transcend the boundaries between natural, mathematical, and ethical disciplines It is called a divine science because it treats of ‘things that are separate from matter in their deWnition and being’ (Metaph 13–15) According to Avicenna, the Wrst ideas that are impressed on the soul are thing, being, and necessary; these cannot be explained by any ideas that are better known, and to attempt to so involves a vicious circle Every thing has its own reality which makes it what it is—a triangle has a reality that makes it a triangle, whiteness has a reality that makes it whiteness: this can be called its being, but a more appropriate technical term is its ‘quiddity’.2 This is a better word because ‘being’ also has the other sense of ‘existence’ The most important division between types of being is that between necessary being and possible being (there is no such thing as impossible being) Possible being is that which, considered in itself, has no necessity to be; necessary being is that which, considered in itself, will be necessary to be What is necessary of itself has no cause; what is of itself possible has a cause A being which had a cause would be, considered in abstraction from that cause, no longer necessary; hence it would not be that which is necessary of itself Whatever, considered in itself, is possible has a cause both of its being and its not being When it has being, it has acquired a being distinct from non-being But when it has ceased to be, it has a non-being distinct from being It cannot be otherwise than that each of these is acquired either from something other than itself or not from something other than itself If it is acquired from something other than itself, that other thing is its cause If it is not acquired The Arabic term is derived from the interrogative ‘What?’; the Latin translators formed a corresponding word, ‘quiddity’, to indicate that which answers the question ‘What (quid) is an X?’ One could form an English term ‘whatness’, but ‘quiddity’ has become suYciently Anglicized over the centuries 190