144-153 (conversation between Strepsiades and a pupil at the "Thinkery," tr. Jeffrey Henderson):
PUPIL. Just now Socrates asked Chaerephon how many of its own feet a flea can jump, because one had bitten Chaerephon's eyebrow and jumped off onto Socrates' head.
STREPSIADES. And how did he measure it off?
PUPIL. Very cleverly. He melted some wax, then picked up the flea and dipped both its feet in the wax, and then when the wax cooled the flea had Persian slippers stuck to it. He took these off and went about measuring the distance.
STREPSIADES. Lord Zeus, what subtlety of mind!
Primo Levi, in his essay "The Leap of the Flea," published in Other People's Trades
, tr. Raymond Rosenthal (New York: Summit Books, 1989), pp. 44-48, doesn't mention the supposed investigations of Socrates and Chaerephon, but he does discuss the research of Miriam Rothschild into the physiology of the flea, which enables it to jump up to a hundred times its own length. Levi defends such studies (p. 48):
Some readers will ask what is the use of all this research: a religious spirit might answer that the harmony of creation is mirrored in the flea; a lay mind prefers to say that the question is not relevant and that a world in which only useful things are studied would be sadder, poorer, and perhaps more violent than the world which fate has allotted us. In substance, the second answer is not very different from the first.
Compare these words from A.E. Housman's introductory lecture
at University College, London (1892):
While the partisans of Science define the end of education as the useful, the partisans of the Humanities define it, more sublimely, as the good and the beautiful. We study, they say, not that we may earn a livelihood, but that we may transform and beautify our inner nature by culture....So we find that the two fancied aims of learning laid down by these two parties will not stand the test of examination. And no wonder; for these are the fabrications of men anxious to impose their own favourite pursuits on others, or of men who are ill at ease in their conscience until they have invented some external justification for those pursuits. The acquisition of knowledge needs no such justification: its true sanction is a much simpler affair, and inherent in itself. People are too prone to torment themselves with devising far-fetched reasons: they cannot be content with the simple truth asserted by Aristotle: 'all men possess by nature a craving for knowledge', πάντες ἄνθρωποι τοῦ εἰδέναι ὀρέγονται φύσει. This is no rare endowment scattered sparingly from heaven that falls on a few heads and passes others by: curiosity, the desire to know things as they are, is a craving no less native to the being of man, no less universal in diffusion through mankind, than the craving for food and drink. And do you suppose that such a desire means nothing? The very definition of the good, says Aristotle again, is that which all desire. Whatever is pleasant is good, unless it can be shewn that in the long run it is harmful, or, in other words, not pleasant but unpleasant. Mr Spencer himself on another subject speaks thus: 'So profound an ignorance is there of the laws of life, that men do not even know that their sensations are their natural guides, and (when not rendered morbid by long continued disobedience) their trustworthy guides.' The desire of knowledge does not need, nor could it possibly possess, any higher or more authentic sanction that the happiness which attends its gratification.