You’d think that a philosopher could reason out the best way to behave, right? But you’d be wrong, very wrong.

Socrates, the Barefoot Bum
Notoriously ugly, clad in one coat long beyond its years and always shoeless, yet possessed of charisma that made the youth swoon, Socrates was a fixture in the marketplace of Athens. There he would engage people with the Socratic method, beginning with a question that seemed straightforward and easy enough to answer, such as, What is virtue? Never content with the first answer, his irony and follow-up questions would inevitably lead to contradictions or admissions of ignorance on the part of his interlocutors. Socrates rubbed some people the wrong way, though, and was brought to trial on trumped-up charges of impiety and corrupting the youth. Defiant to the end, Socrates suggested that the proper sentence for his -crimes would be free meals at the public expense, as he had done the city good. The jury gave him a hemlock cocktail instead.

Diogenes, a Cynic’s Cynic
Always suspicious of society and philosophers, Diogenes (died ca. 320 BCE) would stop at nothing to make a point. He once ripped the feathers out of a live chicken to disprove Plato’s account of human beings as the only featherless biped. Asked once what wine he liked best, his cynical response was ‘other peoples’.- Alexander the Great, intrigued by stories about Diogenes, sought him out and announced, “I am Alexander the Great. What can I do for you?” “Stand back – you block my light” was Diogenes’ response. While the ordinary person would have lost his head after such an insult, Diogenes was admired all the more, as the great conqueror said, “If I were not Alexander, I would be Diogenes.”

Peter Abelard (1079-1144), The Castrated Cleric
Sex scandals are nothing new to the Catholic Church. Take the case of Abelard, the influential medieval philosopher who, ironically, did important work in ethics and logic. The young cleric fell in love with a beautiful young girl named Heloise, whom he was supposed to be tutoring, and they married secretly, though they lived apart. Heloise’s uncle, however, mistakenly thought Abelard had discarded Heloise by placing her in a convent, and he took revenge by having servants castrate Abelard in his sleep. Abelard woke up and things were never the same between him and Heloise (needless to say, things were never the same between his legs either). The ill-fated pair were, however, reunited in death, buried together at Pere Lachaise cemetery in Paris and immortalized in song by Cole Porter: “As Abelard said to Eloise, ‘Don’t forget to drop a line to me, please’” (from “Just One of Those Things”).

Marx: Big Heart, Skinny Wallet
Unable to find work as a philosophy professor, Karl Marx (1818-1883) plotted a revolution. Working intermittently as a journalist and largely relying on the charity of friends, Marx lost many apartments and even some children for lack of financial resources. Declaring religion “the opiate of the masses,” Marx found no solace in a better world to come, but instead sought to change the one he inhabited. “A specter is haunting Europe,” he said, “the specter of communism. The workers of the world have nothing to lose but their chains.” History reveals that Marx didn’t adequately anticipate capitalism’s ability to shift and change to avoid the revolution, as later workers’ movements won concessions in the form of labor laws, the welfare state and five-day work weeks. So, the next time you sleep late on a Saturday, make sure to give props to the man who made the dream of the weekend off a reality.

Arthur Schopenhauer, Poodle-Loving Pessimist
The ultimate pessimist, Schopenhauer (1788-1860) viewed reality as a malicious trap, believing we live in the worst of all possible worlds. A notorious misogynist, Schopenhauer once pushed a woman down a flight of stairs. Grudgingly, he paid her regular restitution for her injuries until her death, when he recorded in his journal, “The old woman dies, the burden is lifted.” Schopenhauer despised noise but inexplicably had a fondness for something more odious, poodles. A series of disposable poodles were his constant companions for most of his life. Not a pleasant academic colleague, Schopenhauer resented the success of Hegel, whose philosophy he thought was the worst kind of nonsense. Perhaps planning to undo Hegel, Schopenhauer scheduled his course lectures at the same time as Hegel’s. The result, however, was an early retirement for Arthur.

Nietzsche: A Bad Boy Who Wasn’t
One might think he railed against the corrupting influence of Christianity an declared “God is dead,”[ because of his own misery (Nietzsche suffered from migraine headaches and poor digestion, topped off with bouts of insomnia). But the guy whose autobiographical Ecce Homo includes such chapters as “Why I Am So Wise,” “Why I Am So Clever,” and “Why I Write Such Good Books” was actually an unassuming, mild-mannered man. His belief in “the will to power” as the most basic human drive finds little reflection in his own life outside his fantasies. Though he fancied himself a warrior and a ladies’ man, Nietzsche’s military service was brief and unspectacular, and he never had a lover. As a bad boy in college, he may have visited a brothel or two, though. One theory suggests that the insanity that cut his career short and institutionalized him for the last 11 years of his life was the result of untreated syphilis.

Adapted from mental_floss presents: Condensed Knowledge (HarperCollins).