Aristotle and Plato: How Their Philosophies Differ

Plato’s world of forms

According to the Stanford Encyclopedia of Philosophy, Plato held that the world we grasp through the senses is in some sense imperfect: a more real and perfect realm exists, populated by entities called forms or ideas. The underlying distinction runs between the many things that strike us as beautiful or just, say, and the single entity that is truly beauty or justice itself.

Ideas, according to Treccani’s entry on Plato, are forms or essences with their own existence: real entities that give sensible things their reason for being. The soul, for Plato, keeps the ability to recall (anamnesis) the forms it had grasped before birth, while it was still without a body: on this view, to know something is above all to remember it. In the Republic, book VII, Plato tells the famous allegory of the cave: people have lived since childhood chained inside an underground cave, forced to face only forward, while a fire burns behind them and, between the fire and the prisoners, a raised walkway carries figures that cast shadows on the wall ahead. The prisoners see only those shadows, and for them the shadows are the whole of reality.

Plato was born in Athens, according to Treccani, in 428 or 427 BCE and died in the same city in 348 or 347 BCE; the Stanford Encyclopedia of Philosophy instead gives 429 BCE as his birth year, marked with a question mark in the entry itself. In 387 BCE Plato founded the Academy, a religious community devoted to the cult of the Muses that doubled as a center of philosophical debate.

Aristotle’s critique

According to the Stanford Encyclopedia of Philosophy, Aristotle takes on Plato’s theory of forms in the Nicomachean Ethics (1096a11-16), where he says the inquiry is unwelcome to him because the people who introduced the forms were his friends. For Aristotle, form is the purpose (telos) of a thing, built into the matter of that very thing. Treccani’s entry on Aristotle calls this immanent form: what in Plato was the idea, eternal and separate, for Aristotle takes shape inside matter and gives rise to the single, concrete thing.

Practical example: think of a table. For Plato, somewhere out there exists the perfect, unchanging idea of “table,” and the wooden piece of furniture in your home is only an imperfect copy of it. For Aristotle, instead, the table points to no world beyond itself: its form, being a flat surface on legs built to hold objects, already sits entirely inside that piece of worked wood.

The break with his teacher, though, was never a personal split. Aristotle studied under Plato at the Academy for close to twenty years, according to Treccani, staying until Plato’s death in 347 BCE; the same source reports that he kept, despite rumors to the contrary, a deep friendship and admiration for his teacher. After Plato’s death, though, Aristotle could not lead the Academy: as a foreign resident in Athens, he was legally barred from its leadership, which passed instead to Speusippus, Plato’s nephew and an Athenian citizen. Aristotle also left Athens as anti-Macedonian feeling grew with the expansion of Philip of Macedon; he had moved to the city, by some accounts, at age seventeen, while other sources put it at eighteen.

Two theories of knowledge

Aristotle’s method, according to the Nicomachean Ethics (1145b2-7) as cited by the Stanford Encyclopedia of Philosophy, starts from observing phenomena and from the opinions gathered about them, before turning to theoretical difficulties. In the Topics (100b21-23), Aristotle calls these shared opinions endoxa: what is accepted by everyone, by the majority, or by the wise, and he uses them as a starting point for reasoning. In the Posterior Analytics he then ties genuine scientific knowledge to grasping the cause that makes a thing what it is (71b9-16), even though the immediate premises, the first principles, cannot themselves be proven (72b21-23).

Plato proceeds differently: he starts from the forms, and the task of knowledge is to climb back from what appears to what truly is. According to the Internet Encyclopedia of Philosophy, compared with Plato and Socrates, Aristotle’s approach was more empirical, grounded in observation: it is one of the reasons he is remembered above all for rejecting Plato’s theory of forms.

Politics: the philosopher-king versus the political animal

In the Republic, book V, Plato has Socrates say that cities will have no rest from their troubles until philosophers become kings, or kings and princes take on the spirit and ability of philosophy: the Smithsonian American Art Museum cites the line in connection with an artwork built around it. This is the core of the philosopher-king thesis: in the ideal city of the Republic, only those who possess knowledge of the forms should take charge of politics, in a regime the Stanford Encyclopedia of Philosophy describes as antidemocratic.

Aristotle looks at politics from another angle. For him, according to the Stanford Encyclopedia of Philosophy’s entry on his political theory, human beings are by nature political animals (zoon politikon), who want to live together in a community; the task of the statesman and the lawgiver concerns the city-state, the polis, as a whole. Aristotle also starts from observing real constitutions, alongside the ideal model, and treats reforming an existing constitution as a task of politics just as important as setting up a new one. He then separates correct constitutions, aimed at the common good, from deviant ones, aimed only at the advantage of whoever governs: monarchy and aristocracy, with their corrupted versions tyranny and oligarchy, plus polity or democracy, six forms in all.

Two different philosophies, no winner

Plato and Aristotle remain two different systems of thought, born in the same place and partly from the same question that the pre-Socratic philosophers had already asked about the ultimate nature of things. The Academy and the Lyceum stood for decades, in the same city, as two radically different ways of doing philosophy, founded roughly fifty years apart.

Centuries later, Raphael painted the two philosophers side by side in the fresco The School of Athens, at the Vatican Museums. Plato stands at the center holding his book, the Timaeus; beside him Aristotle holds the Ethics.