Armand D'Angour suggests that reports (such as that recounted in Plato's Symposium) of Socrates, in about 429 BC, standing perfectly still for hours on end during the Athenian campaign against Potidaea while seemingly deep in thought, are 'too extreme to be considered wholly a matter of rational choice,' and that 'it is reasonable to suppose that it was the symptom of an underlying physiological or psychological condition', such as catalepsy.