Watching the wreckage of the
country EU protectorate known as Greece from afar (and, by the way Thomas Geoghegan, I was born on the right continent, thank you very much), I've seen the following anecdote about Diogenes making the rounds, most recently on reddit:
One day Diogenes sat on the threshold of a random house, eating a plate of lentils. There was not, in all of Athens, a cheaper food available. In other words, if you ate lentils, you were in absolute poverty.
An emissary of the prince approached him and said: "Oh, Diogenes! If you were not so insubordinate and just learned how to flatter a little, you would not be forced to eat lentils."
Diogenes stopped eating, looked up, and replied: "Oh, my brother! If you learned to eat lentils, then you would not be forced to obey and to flatter the prince."
Plato was discoursing on his theory of ideas and, pointing to the cups on the table before him, said while there are many cups in the world, there is only one idea of a cup, and this cupness precedes the existence of all particular cups. "I can see the cup on the table," interrupted Diogenes, "but I can't see the cupness". "That's because you have the eyes to see the cup," said Plato, "but", tapping his head with his forefinger, "you don't have the intellect with which to comprehend cupness." Diogenes walked up to the table, examined a cup and, looking inside, asked, "Is it empty?" Plato nodded. "Where is the emptiness which precedes this empty cup?" asked Diogenes. Plato allowed himself a few moments to collect his thoughts, but Diogenes reached over and, tapping Plato's head with his finger, said "I think you will find here is the emptiness."
Diogenes was once asked what he thought of Socrates. "A madman," he replied. Later, Plato was asked what he thought of Diogenes. "A Socrates gone mad," he replied. Diogenes ridiculed Plato for being long-winded.
Some strangers to Athens once asked Diogenes if he would point out to them the great philosopher (i.e., Plato). Diogenes looked around and then led them to the most deserted part of the city and, gesturing to the empty air as one would in formal introduction, said, "May I present to you the great philosopher Plato."
Plato had just defined Man as an animal, biped and featherless, and was applauded. Diogenes plucked a fowl and brought it into the lecture-room with the words, "Here is Plato's man." Plato was forced to amend his definition by adding quickly: "and having broad nails."
So what's wrong with Plato? Plato thought of the world as fitting into neat, hierarchical categories.
It's fine as an abstract guideline, but if it's taken too literally (as most Platonists are wont to do), it quickly becomes a mental straitjacket, fooling us into thinking that we understand more than we do.
It's no coincidence that pseudo-intellectuals and know-it-alls love Plato; his ideas are also appealing to central planners and bureaucrats.
Take, for instance, how basketball players are selected for China's national team: scouts look for height and physical stature first. Aptitude for (or even interest in) basketball is irrelevant, because the system will drill and discipline athletes, forming them into competent players.
It sounds logical and correct, but it doesn't work in practice.
Doctors in the midst of the scientific arrogance of the 1960s looked down at mothers' milk as something primitive, as if it could be replicated by their laboratories - not realizing that mothers' milk might include useful components that could have eluded their scientific understanding - a simple confusion of absence of evidence of the benefits of mothers' milk with evidence of absence of the benefits (another case of Platonicity as "it did not make sense" to breast-feed when we could simply use bottles). Many people paid the price for this naïve inference: those who were not breast-fed as infants turned out to be at an increased risk of a collection of health problems, including a higher likelihood of developing certain types of cancer - there had to be in mothers' milk some necessary nutrients that still elude us. Furthermore, benefits to mothers who breast-feed were also neglected, such as a reduction in the risk of breast cancer.
So Diogenes was less concerned about coming across as a jackass (though it does make me laugh to think that he once said "Well, I also get my hair cut in a barber's shop" in reply to being scolded about drinking in a tavern) than pointing out that Platonic pretensions towards knowledge serve no useful purpose.