Against scholars who characterise the trial of the life of pleasure in Philebus 20b-21d as a digression or a case of Socrates cheating, I argue that it is a thought experiment containing an important argument in the form of a reductio of the hypothesis that a life could be most pleasant without any cognition. It proceeds in a series of ordered steps, culminating in the precisely chosen image of the jellyfish. Understanding the ancient cultural resonance of this peculiarly plant-like creature yields new insight into Plato's views on the minimal conditions for pleasure.
