Left to my own devices at lunch time, I set a spoon on fire while making soup. Rather than panicking, I efficiently dunked the spoon in the soup and stirred. And now I have a master chef tip for improving a can of Campbell’s vegetable soup. It was a delicious creation with just a hint of smokey goodness. As Protagoras says, “Man is the measure.”

In Plato’s Theatetus, Socrates explores the question, “what is knowledge?” And in the first part of the dialogue he and Theatetus, a boy who has been graced with the same strange face as Socrates, take on Protagoras’s account that all of knowledge is perception. The cause of this is the ever changing nature of the material world, a burning spoon being a great example. One moment it is a normal kitchen tool. In the next it declares my incompetence.  If everything is always changing and nothing is stable, the only knowledge that can exist is our perception of things as they exist in the instance we perceive them. Further, as we all perceive things differently, we each know the world in different ways. So I can authoritatively say that my burnt spoon soup was delicious. I am, as Protagoras says, the measure.

For those of us who prefer certainty to seemingly airy nothingness, Protagoras’s account is unsettling. Philosophically, it means that nothing is true in and of itself. Instead, because everything is in constant motion, all we can hope is to know is what is true at this moment, and even this only means knowing what is true at this moment for me, realizing that it will be different for you and for you and for you. Politically and morally, it raises the real possibility that we treat the world and one another unjustly. After all, if I am the measure, why should I worry about how you feel or what you think?

Yet, in the midst of this discussion, Socrates gives us a reason to hope for more. For although the mutability of the world and of our perception might encourage some to tyranny, for others it reveals the necessity of compassion and friendship. As Socrates says to Theatetus, “I believe the only thing left is for us to be for one another if we are, or if we become, to become for one another, since necessity binds our being together and it binds it to nothing else of all the rest, not even to ourselves, so it’s only left that it has become bound with one another”(160b). 

In other words, if all of knowledge is what we perceive, and it’s easier perceive things externally to ourselves, then Protagoras’s account of the world is necessarily one of community. Things of the world, including ourselves, are constantly changing and becoming other than what they are right now and the way that we know this is by perceiving these changes around us. As a result, our very nature demands an openness to the world around oneself, including the becoming of others. So we are bound, as he says, to become for each other.

In the Ethics, Aristotle ties this understanding directly to friendship. For having explained the nature of virtue and detailed various kinds of virtues, Aristotle turns finally to friendship, for it is only with the help of of our friends that any virtue is possible. Tying perception and understanding together, Aristotle argues that while the virtuous person takes pleasure in perceiving and thus understanding his own life, he takes as much if not more pleasure in perceiving the goodness of his friend, saying, “The excellent person is related to his friend in the same way as he is related to himself, since a friend is another himself… He must, then, perceive his friend’s being [with his own, living together and sharing in conversation and thought]”(1170b).

Recognizing that the material order, at least, is one of constant change, both Plato and Aristotle suggest that we seek to change for the bettter, and love is the impetus of this motion. After all, if all that can be know about you is found in the perception of others, and those closest to us have the best seats to the movement of our lives, then wouldn’t we want to engender in them joy rather than despair?  And so when Socrates first sits down to talk to Theatetus, he stares into Theatetus’s face so as to be able, he says, to examine himself (144e). He can only know himself by means of what he perceives in Theatetus. And as Theatetus will change in the course of their conversation, Socrates can know the effect that his presence and friendship have had on the young boy.  As he says, we are bound by necessity to become for each other.