 The Stoics met these arguments by first pointing out that Heracles’ inability to distinguish cognitive from incognitive impressions in his madness says nothing about the capacities of normal human beings. It is no part of their thesis that just anyone can distinguish between cognitive and incognitive impressions. Their response to the second line of attack was two-fold. The first is a metaphysically motivated answer: if any two objects really were indistinguishable, they would be identical. This doctrine has come to be known as the identity of indiscernibles. They also replied that the Stoic sage would withhold assent in cases where things are too similar to be confident that one had it right (Cicero, 40I) – Sphaerus’ response to his predicament was to say that he only assented to the proposition that it was ‘reasonable’ that what he was presented with were pomegranates (and that was true!).