From Socrates, Plato, and Aristotle, to Nietzsche the list of famous philosophers whose ideas have reverberated throughout history is vast.
Philosophers played and continue to play an important role in society by providing new perspectives, questioning assumptions, and analyzing complex issues. They are responsible for exploring fundamental questions about reality, knowledge, ethics, and the nature of existence and by doing help to shape our understanding of the world.
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Born in Athens in 469 BCE, Socrates is widely considered to be the foundational figure in Western philosophy. Intelligent, well-educated, and an accomplished military veteran, he nonetheless was an eccentric figure in his day. Though he came from a reasonably affluent family, the ancient Greek philosopher didn’t trim his hair, rarely washed, and commonly loitered in the agora, or marketplace, barefoot in a simple tunic and speaking to anyone willing to stay and talk to him. In a society that valued refinement, beauty, and physical perfection, the pug-nosed, usually unkempt Socrates was a strange figure, indeed.
Yet he was popular with the young men of the city and frequently drew a crowd of young students from more affluent backgrounds. It’s from two of these students – Plato and Xenophon – that we receive our accounts of his teachings.
Socrates authored no writings – unsurprising, given that he constantly claimed he knew nothing. His dialectic method – known today as the Socratic method – was to not offer any opinions or premises of his own, but to dissect the arguments of others with increasingly probing questions that exposed the inconsistencies or flaws in their answers.
Unlike many ancient Greek philosophers, Socrates had no interest in either mathematics or the natural sciences. His exclusive concern was with the soul – morality, virtue, and the proper way to live. To that end, he would take the role of a so-called ignorant inquisitor, questioning others on concepts such as love, piety, and justice – never seeming to reach a conclusion himself, yet illuminating the subject through the back and forth of his interrogation.
The Death of Socrates
While Socrates’ earned the admiration of much of the city’s youth, his eccentricity and nonconformity earned a number of critics and enemies as well. The playwright Aristophanes presented Socrates as an oaf and a swindler in his Clouds – and he was not the only writer to portray the philosopher negatively.
Socrates took strong moral stands, which made enemies both when his name was drawn to serve in the Athenian assembly and later when the Thirty Tyrants (installed by Sparta after the Peloponnesian War) ruled the city. And though he seemed to have at least some belief in the Greek gods, his sometimes unconventional expressions of that belief led to more than one accusation of impiety.
But more critically, he was accused of supporting Spartan-like authoritarianism in favor of Athens’ democracy. A number of his students had defected to Sparta – two former students were even among the Thirty Tyrants – and while pro-Spartan sentiment was not unusual among young people from affluent Athenian families, the incriminating association proved fatal.
In 399 BCE, Socrates was convicted of corrupting the city’s youth in a rapid trial and sentenced to drink a poisonous brew of hemlock. As described by Plato (whose Apology records a supposed account of the trial), Socrates was in good spirits, and – having refused an earlier offer of escape from his allies – accepted the drink without protest and died surrounded by his friends.
The most famous of Socrates’ students, Plato is a renowned Greek philosopher in his own right. As 19th Century philosopher Alfred North Whitehead noted, “the safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato.”
Born to an aristocratic Athenian family around 427 or 428 BCE, his actual name is reported to have been Aristocles – Plato, or Platon, was a wrestling nickname meaning “broad-shouldered.” Like many of the city’s affluent youth, he became an admirer and student of Socrates and is the primary source of his teacher’s technique and ideas.
For years after Socrates’ death, Plato studied with philosophers in Italy and northern Africa including Pythagoras, Zeno, and Theodorus of Cyrene. He then returned to Greece to do something Socrates never did – become a self-professed teacher.
Near Athens was the sacred grove of the Greek hero Academus, which became the site of Plato’s school, the Academy. Founded in 387 BCE, the Academy drew students from across ancient Greece – and many from outside it – and would endure for some three hundred years before it was destroyed by the Roman general Sulla in 84 BCE.
Plato’s writings were almost exclusively in the form of dialogues. Rather than straightforward treatises on a given subject, he would present his ideas in the form of a discussion between characters – chiefly Socrates, through which we have our best view of the philosopher.
The earliest dialogues, such as Crito, are regarded as giving an accurate picture of Socrates’ teachings. Plato’s later dialogues, however, seem to show an “evolution” of Socrates as the dialogues increasingly became a vehicle to express his own ideas. In later writings like Timeaus, Plato still ostensibly used the dialogue format, though the actual text becomes dominated by deep dives into different topics.
Form and Function
Plato espoused the idea of perfect Forms of all things. Every table, for example, expressed some degree of “table-ness,” but none could ever achieve the perfection of the true Form – the physical world could offer only pale imitations.
This was laid out in Plato’s most famous work, The Republic. In a parable called “The Allegory of the Cave,” a group of people spends their entire lives chained to the wall of a cave. As objects pass behind them, the shadows of those objects are projected onto the blank wall before them – the people never see the objects themselves, just the shadows, which they name and which define their understanding of reality. The Forms are the real objects, and the shadows on the wall are the approximations of those objects that we understand with our limited senses in the physical world.
The Republic itself is an examination of what defines both a just man and a just society. Perhaps Plato’s most influential work, it touched on rulership, education, law, and political theory, and inspired notables from the Roman Emperor Gratian to the 16th Century philosopher Thomas More to, somewhat ironically, the fascist dictator Mussolini.
No student of Plato’s Academy is more famous today than Aristotle. Born in Stagira in Northern Greece in about 384 BCE, he journeyed to Athens and joined the Academy when he was about eighteen. He would remain there for the next nineteen years.
He left Athens for Macedonia shortly after Plato’s death, at the request of King Phillip II, who wanted Aristotle to tutor his son, Alexander – known later as Alexander the Great. For almost a decade he would remain in this role before returning to Athens in about 335 BCE and founding his own school, the Lyceum.
For twelve years, Aristotle taught at the Lyceum, and in this period created the bulk of his works – though most have sadly not survived into the modern age. But in 323 BCE, he would be forced to flee the city.
The relationship between Aristotle and his former pupil, Alexander, had soured over Alexander’s close relationship with Persia and Persian culture. But when Alexander died suddenly in June of 323 and a wave of anti-Macedonian sentiment swept across Athens, Aristotle’s history with Macedonia still earned him accusations of impiety.
Unwilling to risk a repeat of Socrates’ trial and execution, Aristotle fled to the estate of his mother’s family on the island of Euboea. He died the following year, in 322 BCE. His Lyceum continued under the direction of his students for a few decades, but it ultimately faded away in the shadow of the more successful Academy.
The Legacy of Aristotle
Much of Aristotle’s work has been lost, but what remains demonstrates the breadth of his intellect. Aristotle wrote on subjects from government and logic to zoology and physics. Among his surviving works are accurate anatomical descriptions of animals, a book on literary theory, treatises on ethics, records of geological and astronomical observations, writings on politics, and the earliest outlines of the scientific method.
One of his most critical surviving works is the Organon, a collection of works on dialectical methods and logical analysis. Providing the basic tools for scientific and formal logical inquiry, these works heavily influenced philosophy for almost two millennia.
Another key work would be the Nicomachean Ethics, a study of ethics that became the core of medieval philosophy, and in turn, heavily influenced European law. In Book II of the Nicomachean Ethics, Aristotle introduces his version of the Golden Mean – a concept in which morality and virtue are thought to lay in the balance. That is, virtue is only a virtue when it is taken to the proper level – in either excess or deficiency, it becomes a moral failing, as when courage becomes recklessness (excess) or cowardice (deficiency).
Fully quantifying Aristotle’s impact would be a momentous task. Even in his surviving works – a fraction of his full portfolio – he made significant contributions to almost every intellectual discipline of the time.
His work was so significant that medieval Arabic scholars called him “the First Teacher.” In the West, meanwhile, he was often called simply “the Philosopher,” while the poet Dante dubbed him “the master of those who know.”
A century before Socrates set the foundations of Western philosophy, a Chinese philosopher did the same in the East. Born in 551 BCE in what is now the Shandong province of China, his name was Kǒng Zhòngni, also known as Kǒng Fūzǐ, or “Master Kong” – Latinized by 16th Century missionaries into the name we now know, “Confucius.”
He was born into an era known as the Warring States Period, during which the long prosperity of the Zhou dynasty gave way to an array of contender states that waged hundreds of wars against each other over the span of 250 years. But the political chaos of the time didn’t eclipse the great intellectual legacy of the Zhou dynasty, particularly the texts known as the Five Classics. This scholarly heritage fueled a class of learned men like Confucius – and such learned men were in demand by warlords who sought wise counsel to give them an advantage over their rivals.
Confucius spent years serving in a series of government postings in the state of Lu before power struggles forced his resignation. He then spent 14 years wandering the various states of China in search of a ruler to serve who would be open to his influence and moral guidance. He presented himself not as a teacher, but rather as a conveyer of the lost moral principles of an earlier age.
He didn’t actively seek disciples during his time in government, though he drew them just the same – young men from all backgrounds hoping to learn from his example and teachings to further their own careers. And a small number of them even followed Confucius into his wandering exile.
In 484 BCE, Confucius returned to Lu in response to a request (and generous monetary enticement) from the chief minister of the state. While he occupied no official position on his return, the ruler and his ministers frequently sought his advice. The number of his disciples expanded considerably, and the sage devoted himself to teaching until his death in 479 BCE.
Like Socrates, Confucius left no writings of his own. We know of his teachings only through his students, chiefly in the form of the Analects, a compendium of individual sayings, dialogues, and ideas compiled by his disciples and refined over the century or so after his death.
Confucianism occupies a foundational place in the culture of countries across Asia and hinges on a set of five constant virtues, which together lead to a moral, harmonious, and successful life. The first is Ren, or Benevolence, kindness to oneself and to others without expectation of reward. This is followed by Righteousness (Yi), the moral disposition to do good and the understanding to do so. The third virtue is Li, or Propriety – the embrace of etiquette, social ritual, and obligation – especially to family members, elders, and authorities.
Next is Zhi, or Wisdom, a combination of knowledge, good judgment, and experience that guides one in their moral decisions. And last is Fidelity or Trustworthiness (Xin), the cultivated reputation for integrity and reliability that wins the faith of others. And in line with these virtues was the Golden Rule of Confucianism, centuries before its expression in Christianity – do not do unto others what you would not want others to do unto you.
A rough contemporary of Confucius, Sun Tzu, or “Master Sun” (whose actual name was said to be Sun Wu), was a legendary military strategist. When the battles of the Warring States Period fell into stalemates due to a universal reliance on the same traditional tactics and protocols, he reinvented military strategy and operations.
He is traditionally believed to have been born in 544 BCE, in either the Wu or Qi states in eastern China. The chaos of the period makes historical documentation spotty, though he is thought to have served as a general for the ruler of Wu beginning sometime around 512 BCE.
It should be noted, however, that there is at least a possibility that he was not a historical figure at all. His supposed name, Sun Wu, effectively translates to “fugitive warrior,” and his only documented battle, the Battle of Boju, has no record of him – indeed, he isn’t mentioned in historical records until centuries later.
This makes it at least possible that Sun Tzu was a pen name for an unnamed military expert – or perhaps a group of them. Again, however, historical records of the time are incomplete, leaving the historicity of Sun Tzu uncertain one way or the other.
The Art of War
Sun Tzu’s fame rests on the single work attributed to him, The Art of War. Like Sun Tzu himself, the historical basis of the book is uncertain, though at least the earlier portions of it are believed to have been written in the 5th Century BCE – though other portions may not have appeared until much later.
The Art of War is divided into 13 chapters, covering subjects such as the fluidity of the battlefield environment, the value of timing, common situations found in battle, the importance of information, and more. Though not a religious text per se, the principles of Taoism infuse the teachings of The Art of War, and it is clear the author saw the ideal general as one who had mastered Taoist thought.
The book became the foundation of early Chinese military strategy and likewise became revered among Japanese generals (and later, the samurai) after its introduction to the country around 760 CE. It has been studied and applied by military leaders around the globe (and today is included in the instructional materials of the US Army Academy at West Point) and has proved equally applicable to conflict and competition outside the military arena, such as business, politics, and sports.
Augustine of Hippo
Aurelius Augustinus, later to be known as Augustine of Hippo (and later St Augustine), was born in 354 CE in Tagaste in Numidia (modern-day Algeria), at the very edge of the Roman Empire’s reach in North Africa. His parents were Roman citizens of respectable but middling means yet were able to provide their son with a top-tier education, sending him off to study in both Madauros (Numidia’s largest city) and Carthage.
At 19, he became an adherent of Manichaeism, a Persia-based dualistic religion that had originated in the 3rd Century CE and quickly rose to become Christianity’s chief rival. He followed Manichaeism for nine years, to the chagrin of his mother (a devoted Christian who had baptized Augustine at an early age).
In 383 he took a position as a professor of rhetoric in Milan, and there came under the sway of the theologian Ambrose of Milan and other Christians who exposed Augustine to an intellectual Christianity flavored with Neoplatonism. As a result, Augustine abandoned Manichaeism, converted to Christianity, and resigned from his post in 386, returning to Tagaste just a few years later. After a brief period of listlessness, he was apparently pressed into service in the clergy in the nearby coastal city of Hippo in 391 and succeeded the bishop there just four years later – a post he would hold until his death.
Augustine was one of the most prolific philosophic writers in history. Over the thirty-five years he served as bishop of Hippo, he wrote extensively, producing over five million words that have survived (and likely more that haven’t).
Fed by the twin streams of Platonism and Christianity, Augustine wove both together in an intellectual faith that operated with reason, allowed for allegory and metaphor in scriptural interpretation, and held that truth was found by turning the mind inward – yet still incorporated Christian ideas of sin, redemption, and that illumination was provided by God alone. The ideas of this influential philosopher would heavily influence the fledgling Roman Catholic church, as well as the later Protestant thought.
Of all of Augustine’s writings, perhaps none is quite as important as his Confessions, written between 397 and 400 CE. An unflinching account of his own early life and spiritual journey, it is widely regarded as the first true autobiography in Western Christian literature and influenced both medieval Christian writers and later philosophers.
His other most famous work is On the City of God Against the Pagans, known more commonly as the City of God. Written in the aftermath of the Visigoths’ sack of Rome in 410, the book was meant as a vindication of Christianity (blamed by some for the fall of Rome), as well as a consolation and source of hope for Christians across the Empire.
Another Germanic tribe, the Vandals, would lay siege to Hippo in 430 CE. Augustine fell ill during the siege and died prior to the razing of the city. He was canonized by the church in 1303 and declared Saint Augustine by Pope Boniface VIII.
The French philosopher known as the father of modern philosophy, René Descartes, was born in the province of Touraine in west-central France in March of 1596, the son of a member of the Parliament of Brittany (similar to a court of appeals). He studied at the Jesuit Collège Royal Henry-Le-Grand, where he developed a fondness for the certainty of mathematics, and then – in accordance with his father’s wishes – received a law degree from the University of Poitiers in 1616.
He already knew he did not wish to follow this path, however – his education had shown him how much was unknown, in doubt, or disputed, and he resolved henceforth to learn only from real-life experience and his own reason. This decision, coupled with his admiration for mathematics would form the basis of his later works.
He joined the Dutch States Army as a mercenary in 1618, further pursuing mathematics by studying military engineering. During this time, he also met the Dutch scientist and philosopher Isaac Beeckman, with whom he collaborated on work in both physics and geometry.
He would return to France two years later, when his military service ended, and began work on his first philosophical treatise, Rules for the Direction of the Mind. This work, however, was never completed – though he returned to it more than once over the years – and the unfinished manuscript would not be published until after his death.
After converting his inherited property into bonds – which provided him a lifetime income – Descartes returned to the Dutch Republic. After further studying mathematics at the University of Franeker, he devoted the next two decades to writing on science and philosophy.
Cogito, Ergo Sum
Descartes espoused a philosophical theory known today as Cartesianism, which sought to abandon anything that could not be known without certainty, then build upon only what remained to find the truth. This philosophy built upon and expanded Aristotle’s ideas of foundationalism, interjecting Descartes’ love of mathematical certainty into Western philosophy.
This new form of philosophy, called rationalism, trusted only the power of deductive reason – the senses can lie, and only the mind can be a source of truth. This led to Descartes’ foundational truth, expressed in 1637 in his Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth in the Sciences – more commonly known simply as Discourse on the Method – with the simple phrase Cogito, ergo sum – “I think, therefore I am.”
The very act of doubting requires an existing mind with which to doubt, therefore the existence of that mind is an a priori assumption – the first solid truth upon which one can build. This break with classic Aristotelian philosophy and its assumption that the senses provided valid evidence in favor of a more skeptical, reason-based approach has earned Descartes the title “the father of modern philosophy.”
He is likewise known as the father of modern mathematics for his development of analytical geometry and the invention of the Cartesian coordinates system, among other advances. Further developed by others after his death, Descartes’ mathematical advances were instrumental to modern physics and other scientific disciplines.
He spent his last years as a tutor of Queen Christina of Sweden, though the two apparently did not get along. The cold climate coupled with early mornings (he was required to give lessons at 5 am, after a lifetime of sleeping until almost noon due to fragile health) caused him to contract pneumonia, from which he died in February 1650.
Friedrich Nietzsche was born in 1844 near Leipzig in Prussia (now Germany). His father, a Lutheran minister, died when Nietzsche was five, and his family subsequently moved to Naumberg in central Germany.
He had an exemplary academic career, and in May 1869 was named Professor of Greek Language and Literature at Switzerland’s University of Basel. He was only 24 years old and had not yet attained his doctorate – the youngest person ever appointed to that post.
Yet even at the time of his appointment, his study of language was beginning to be supplanted by philosophical ideas. This comes through in his first book, The Birth of Tragedy out of the Spirit of Music, published in 1872. Far from a treatise of dutiful scholarship, the book was an opinionated, controversial argument about the decline of Athenian drama and the modern ascension of works like those of Wagner (whom Nietzsche had befriended when he was a university student in Leipzig).
He continued writing in this vein with four essays – collectively known as the Untimely Meditations – published between 1873 and 1876. These essays show the early framework of Nietzsche’s philosophy – elitism, the human drive for power, the obsolescence of Christianity in the modern world, and the subjectivity of truth.
In 1879, Nietzsche – from a combination of failing health, a diminished academic reputation as a philologist, and a loss of the university’s support – resigned from his professorship. Unconstrained, he now began writing philosophical works in earnest, and in the following years published the three-part Human, All Too Human (the first part of which he published prior to leaving the university, in 1878), Thus Spoke Zarathustra, Beyond Good and Evil, and more.
Though the term didn’t exist in his own time, Nietzsche is now considered an existentialist philosopher – eschewing the otherworldliness and absolute truths of religious thinking and rejecting the elevation of reason over the direct information of the senses. Meaning, like truth and morality, is subjective and determined by the individual – man defines his world by an act of will.
Nietzsche envisioned an “overman,” or Übermensch (first described in Thus Spoke Zarathustra), a superior human who had mastered himself, abandoned outdated absolutist confines like religion and crafted his own values and meaning for life. The concept – and other aspects of Nietzsche’s work – would be later misused by the Third Reich. which made frequent use of the Übermensch idea.
Nietzsche himself had disdained nationalism as contrary to the idea of self-determination and was strongly opposed to anti-Semitism. Unfortunately, after his death, his sister Elisabeth (an ardent German nationalist) took control of his works and compiled his unpublished writings (with a great deal of “adjustment”) into Will to Power, posthumously published under his name but now regarded as more indicative of her ideas than that of the German philosopher.
Nietzsche – who’d struggled with physical and mental health problems for most of his life – suffered a mental breakdown in 1889 at the age of 44. Over the following years, he progressed rapidly into dementia, suffered at least two strokes which left him utterly incapacitated, and died in August of 1900.