Saloni de Souza

The relationship between Aristotle and Plato has long been characterised as one of conflict and rejection.  Initially Plato’s star pupil, Aristotle began to question and challenge many Platonic views, eventually rejecting them altogether in his own work – or so the story goes.  This story has fallen out of favour in recent scholarship and there have been attempts to read Aristotle as being in conversation with Plato and not at war with him.  In my thesis I strengthen the case for rejecting the old picture of Aristotle's relationship with Plato by examining two much neglected texts: Part II of Plato’s Parmenides and Aristotle’s Metaphysics, Iota. I concentrate on problems of identity and non-identity and have two other goals: to further our understanding of identity and non-identity in these texts, thereby uncovering interesting lessons for the study of Plato and Aristotle more generally, and to unearth interesting and important lessons from these texts for contemporary debates about numerical identity.  

 

I am primarily concerned with three problems.  The first stems from the fundamental question that philosophers who are interested in numerical identity in both contemporary and ancient philosophy are concerned with: what is it that makes something one and the same thing (i.e. identical to itself) and different from (i.e.  non-identical to) other things?  On first reflection, this seems an entirely trivial thing to ask; surely obvious that everything is identical to itself and non-identical to anything else?  However, thinking more deeply about this question reveals real problems. Consider the following case.  On Monday, when I was cycling, I noticed that my bicycle tyre had a puncture.  On Tuesday, I replaced the tyre.  Is it still the same bicycle?  

 

One answer is that it is not, since it has changed.   A serious problem with this answer is that it forces us to accept that whenever anything undergoes any change whatsoever, however small, it becomes a different thing.  Yet, this seems utterly implausible.  For example, it seems ludicrous to claim that if on Tuesday, my bicycle has a speck of rust on it that was not there on Monday, my bicycle on Tuesday is not identical to my bicycle on Monday.  How we can reconcile this answer with our ordinary ideas about what counts as one and the same thing and if so, how, is a problem that continues to occupy contemporary philosophers.  

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In my thesis, I argue that the definitions of identity and non-identity that Plato provides in some passages of Part II of the Parmenides suggest that the above answer is right.  As such, the very same problem arises.  I argue that Plato’s close connection between identity and non-identity and similarity and dissimilarity points to a strategy that both he and contemporary philosophers might use to solve the problem: it is true that whenever anything undergoes any change, however small, it becomes a different thing.  Nevertheless, we can explain why it might seem that my bicycle is the same thing even if it develops a tiny speck of rust: the bicycle without the speck of rust and the bicycle with it are very similar.  I then examine Metaphysics, Iota and argue that Aristotle would reject the idea that whenever anything undergoes any change, it becomes a different thing.  I argue that his connection between identity, non-identity and similarity and dissimilarity yield a possible strategy that we might use to show that the Platonic solution is problematic: similarity and dissimilarity just do not work like this. 

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The second problem that I deal with concerns an outrageous claim that we might think Plato and Aristotle make in Part II of Plato’s Parmenides and Metaphysics, Iota: there are some things that are neither identical nor non-identical to some things.  This seems patently false, since everything must be identical to itself and non-identical to anything else if it is to be the very thing that it is; if my bicycle exists but is not identical to itself, it must be two different things and if it is exists but is not non-identical to my car, my bicycle and car must somehow end up being one thing.  I argue that whilst Plato points to some things that are difficult to justify as being either identical or non-identical to one another, Aristotle does not in fact believe that there are some things that are neither identical nor non-identical to some things and has a complex and interesting story to tell about why.

 

The third problem I explore concerns identity and relativity.  Relatives for Plato and Aristotle are things like father, bigger, next to, whereas examples of non-relatives are blue and square.  However, identity does not quite work like either of these.  It seems to have the defining characteristic of relatives in that it is said with respect to something; we say something is identical to something, just as we say someone is the father of someone or something is bigger than something.  However, nothing is ever identical with respect to something else, since things are only ever identical to themselves; rather things are identical all by themselves. This seems to be the defining characteristic of non-relatives; things are blue or square irrespective of anything else.  I explore how Plato and Aristotle cope with these discrepancies.