The Philosophy Book

by DK Publishing

  "The soul of man is immortal and imperishable."

  Plato

  Marcus Aurelius, Roman Emperor from 161 to 180 CE, was not just a powerful ruler, he was a noted scholar and thinker—a realization of Plato’s idea that philosophers should lead society.

  Unsurpassed legacy

  Plato himself was the embodiment of his ideal, or true, philosopher. He argued on questions of ethics that had been raised previously by the followers of Protagoras and Socrates, but in the process, he explored for the first time the path to knowledge itself. He was a profound influence on his pupil Aristotle—even if they fundamentally disagreed about the theory of Forms. Plato’s ideas later found their way into the philosophy of medieval Islamic and Christian thinkers, including St. Augustine of Hippo, who combined Plato’s ideas with those of the Church.

  By proposing that the use of reason, rather than observation, is the only way to acquire knowledge, Plato also laid the foundations of 17th-century rationalism. Plato’s influence can still be felt today—the broad range of subjects he wrote about led the 20th-century British logician Alfred North Whitehead to say that subsequent Western philosophy “consists of a set of footnotes to Plato.”

  "What we call learning is only a process of recollection."

  Plato

  PLATO

  Despite the large proportion of writings attributed to Plato that have survived, little is known about his life. He was born into a noble family in Athens in around 427 BCE and named Aristocles, but acquired the nickname “Plato” (meaning “broad”). Although probably destined for a life in politics, he became a pupil of Socrates. When Socrates was condemned to death, Plato is said to have become disillusioned with Athens, and left the city. He travelled widely, spending some time in southern Italy and Sicily, before returning to Athens around 385 BCE. Here he founded a school known as the Academy (from which the word “academic” comes), remaining its head until his death in 347 BCE.

  Key works

  c.399–387 BCE Apology, Crito, Giorgias, Hippias Major, Meno, Protagoras (early dialogues)

  c.380–360 BCE Phaedo, Phaedrus, Republic, Symposium (middle dialogues)

  c.360–355 BCE Parmenides, Sophist, Theaetetus (late dialogues)

  See also: Thales of Miletus • Heraclitus • Protagoras • Socrates • Aristotle • Plotinus • St. Augustine of Hippo

  IN CONTEXT

  BRANCH

  Epistemology

  APPROACH

  Epistemology

  BEFORE

  399 BCE Socrates argues that virtue is wisdom.

  c.380 BCE Plato presents his theory of Forms in his Socratic dialogue, The Republic.

  AFTER

  9th century CE Aristotle’s writings are translated into Arabic.

  13th century Translations of Aristotle’s works appear in Latin.

  1690 John Locke establishes a school of British empiricism.

  1735 Zoologist Carl Linnaeus lays the foundations of modern taxonomy in Systema Naturae, based on Aristotle’s system of biological classification.

  Aristotle was 17 years old when he arrived in Athens to study at the Academy under the great philosopher Plato. Plato himself was 60 at the time, and had already devised his theory of Forms. According to this theory, all earthly phenomena, such as justice and the color green, are shadows of ideal counterparts, called Forms, which give their earthly models their particular identities.

  Aristotle was a studious type, and no doubt learnt a great deal from his master, but he was also of a very different temperament. Where Plato was brilliant and intuitive, Aristotle was scholarly and methodical. Nevertheless, there was an obvious mutual respect, and Aristotle stayed at the Academy, both as a student and a teacher, until Plato died 20 years later. Surprisingly, he was not chosen as Plato’s successor, and so he left Athens and took what would prove to be a fruitful trip to Ionia.

  Plato’s theory questioned

  The break from teaching gave Aristotle the opportunity to indulge his passion for studying wildlife, which intensified his feeling that Plato’s theory of Forms was wrong. It is tempting to imagine that Aristotle’s arguments had already had some influence on Plato, who in his later dialogues admitted some flaws in his earlier theories, but it is impossible to know for certain. We do know, though, that Plato was aware of the Third Man argument, which Aristotle used to refute his theory of Forms. This argument runs as follows: if there exists in a realm of Forms a perfect Form of Man on which earthly men are modelled, this Form, to have any conceivable content, would have to be based on a Form of the Form of Man—and this too would have to be based on a higher Form on which the Forms of the Forms are based, and so on ad infinitum.

  Aristotle’s later argument against the theory of Forms was more straightforward, and more directly related to his studies of the natural world. He realized that it was simply unnecessary to assume that there is a hypothetical realm of Forms, when the reality of things can already be seen here on Earth, inherent in everyday things.

  Perhaps because his father had been a physician, Aristotle’s scientific interests lay in what we now call the biological sciences, whereas Plato’s background had been firmly based in mathematics. This difference in background helps to explain the difference in approach between the two men. Mathematics, especially geometry, deals with abstract concepts that are far removed from the everyday world, whereas biology is very much about the world around us, and is based almost solely on observation. Plato sought confirmation of a realm of Forms from notions such as the perfect circle (which cannot exist in nature), but Aristotle found that certain constants can be discovered by examining the natural world.

  Plato and Aristotle differed in their opinion of the nature of universal qualities. For Plato, they reside in the higher realm of the Forms, but for Aristotle they reside here on Earth.

  Trusting the senses

  What Aristotle proposed turned Plato’s theory on its head. Far from mistrusting our senses, Aristotle relied on them for the evidence to back up his theories. What he learnt from studying the natural world was that by observing the characteristics of every example of a particular plant or animal that he came across, he could build up a complete picture of what it was that distinguished it from other plants or animals, and deduce what makes it what it is. His own studies confirmed what he already believed—that we are not born with an innate ability to recognize Forms, as Plato maintained.

  Each time a child comes across a dog, for example, it notes what it is about that animal that it has in common with other dogs, so that it can eventually recognize the things that make something a dog. The child now has an idea of “dogginess”, or the “form”, as Aristotle puts it, of a dog. In this way, we learn from our experience of the world what the shared characteristics are that make things what they are—and the only way of experiencing the world is through our senses.

  "Everything that depends on the action of nature is by nature as good as it can be."

  Aristotle

  The essential form of things

  Like Plato, then, Aristotle is concerned with finding some kind of immutable and eternal bedrock in a world characterized by change, but he concludes that there is no need to look for this anchor in a world of Forms that are only perceptible to the soul. The evidence is here in the world around us, perceptible through the senses. Aristotle believes that things in the material world are not imperfect copies of some ideal Form of themselves, but that the essential form of a thing is actually inherent in each instance of that thing. For example, “dogginess” is not just a shared characteristic of dogs—it is something t
hat is inherent in each and every dog.

  By studying particular things, therefore, we can gain insight into their universal, immutable nature.

  What is true of examples in the natural world, Aristotle reasons, is also true of concepts relating to human beings. Notions such as “virtue”, “justice”, “beauty”, and “good” can be examined in exactly the same way. As he sees it, when we are born our minds are like “unscribed tablets”, and any ideas that we gain can only be received through our senses. At birth, we have no innate ideas, so we can have no idea of right or wrong. As we encounter instances of justice throughout our lives, however, we learn to recognize the qualities that these instances have in common, and slowly build and refine our understanding of what justice is. In other words, the only way we can come to know the eternal, immutable idea of justice, is by observing how it is manifested in the world around us.

  Aristotle departs from Plato, then, not by denying that universal qualities exist, but by questioning both their nature and the means by which we come to know them (the latter being the fundamental quesion of “epistemology”, or the theory of knowledge). And it was this difference of opinion on how we arrive at universal truths that later divided philosophers into two separate camps: the rationalists (including René Descartes, Immanuel Kant, and Gottfried Leibniz), who believe in a priori, or innate, knowledge; and the empiricists (including John Locke, George Berkeley, and David Hume), who claim that all knowledge comes from experience.

  Aristotle classified many of the different strands of knowledge and learning that we have today, such as physics, logic, metaphysics, poetics, ethics, politics, and biology.

  "All men by nature desire to know."

  Aristotle

  Biological classification

  The manner in which Plato and Aristotle arrive at their theories tells us much about their temperaments. Plato’s theory of Forms is grand and otherworldly, which is reflected in the way he argues his case, using highly imaginative fictionalized dialogues between Socrates and his contemporaries. By contrast, Aristotle’s theory is much more down to earth, and is presented in more prosaic, academic language. Indeed, so convinced was Aristotle that the truth of the world is to be found here on Earth, and not in some higher dimension, that he set about collecting specimens of flora and fauna, and classified them according to their characteristics.

  For this biological classification, Aristotle devised a hierarchical system—the first of its kind, and so beautifully constructed that it forms the basis of the taxonomy still in use today. First, he divides the natural world into living and non-living things, then he turns his attention to classifying the living world. His next division is between plants and animals, which involves the same kind of thinking that underpins his theory of universal qualities: we may be able to distinguish between a plant and an animal almost without thinking, but how do we know how to make that distinction? The answer, for Aristotle, is in the shared features of either category. All plants share the form “plant”, and all animals share the form “animal.” And once we understand the nature of those forms, we can then recognize them in each and every instance.

  This fact becomes more apparent the more Aristotle subdivides the natural world. In order to classify a specimen as a fish, for example, we have to recognize what it is that makes a fish a fish—which, again, can be known through experience and requires no innate knowledge at all. As Aristotle builds up a complete classification of all living things, from the simplest organisms to human beings, this fact is confirmed again and again.

  Teleological explanation

  Another fact that became obvious to Aristotle as he classified the natural world is that the “form” of a creature is not just a matter of its physical characteristics, such as its skin, fur, feather, or scales, but also a matter of what it does, and how it behaves—which, for Aristotle, has ethical implications.

  To understand the link with ethics, we need first to appreciate that for Aristotle everything in the world is fully explained by four causes that fully account for a thing’s existence. These four causes are: the material cause, or what a thing is made of; the formal cause, or the arrangement or shape of a thing; the efficient cause, or how a thing is brought into being; and the final cause, or the function or purpose of a thing. And it is this last type of cause, the “final cause”, that relates to ethics—a subject which, for Aristotle, is not separate from science, but rather a logical extension of biology.

  An example that Aristotle gives is that of an eye: the final cause of an eye—its function—is to see. This function is the purpose, or telos, of the eye—telos is a Greek word that gives us “teleology”, or the study of purpose in nature. A teleological explanation of a thing is therefore an account of a thing’s purpose, and to know the purpose of a thing is also to know what a “good” or a “bad” version of a thing is—a good eye for example, is one that sees well.

  In the case of humans, a “good” life is therefore one in which we fulfill our purpose, or use all the characteristics that make us human to the full. A person can be considered “good” if he uses the characteristics he was born with, and can only be happy by using all his capabilities in the pursuit of virtue—the highest form of which, for Aristotle, is wisdom. Which brings us full circle back to the question of how we can recognize the thing that we call virtue—and for Aristotle, again, the answer is by observation. We understand the nature of the “good life” by seeing it in the people around us.

  Aristotle’s classification of living things is the first detailed examination of the natural world. It proceeds from general observations about the characteristics shared by all animals, and then subdivides into ever more precise categories.

  The syllogism

  In the process of classification, Aristotle formulates a systematic form of logic which he applies to each specimen to determine whether it belongs to a certain category. For example, one of the characteristics common to all reptiles is that they are cold-blooded; so, if this particular specimen is warm-blooded, then it cannot be a reptile. Likewise, a characteristic common to all mammals is that they suckle their young; so, if this specimen is a mammal, it will suckle its young. Aristotle sees a pattern in this way of thinking—that of three propositions consisting of two premises and a conclusion, for example in the form: if As are Xs, and B is an A, then B is an X. The “syllogism”, as this form of reasoning is known, is the first formal system of logic ever devised, and it remained the basic model for logic up until the 19th century.

  But the syllogism was more than simply a by-product of Aristotle’s systematic classification of the natural world. By using analytical reasoning in the form of logic, Aristotle realized that the power of reason was something that did not rely on the senses, and that it must therefore be an innate characteristic—part of what it is to be human. Although we have no innate ideas, we do possess this innate faculty, which is necessary for us to learn from experience. And as he applied this fact to his hierarchical system, he saw that the innate power of reason is what distinguishes us from all other living creatures, and placed us at the top of the hierarchy.

  "Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle."

  Charles Darwin

  “Socrates is mortal” is the undeniable conclusion to the most famous syllogism in history. Aristotle’s syllogism—a simple deduction from two premises to a conclusion—was the first formal system of logic.

  Decline of Classical Greece

  The sheer sco
pe of Aristotle’s ideas, and the revolutionary way in which he overturns Plato’s theory of Forms, should have ensured that his philosophy had a far greater impact than it did during his lifetime. That is not to say that his work was without fault—his geography and astronomy were flawed; his ethics supported the use of slaves and considered women to be inferior human beings; and his logic was incomplete by modern standards. However, what he got right amounted to a revolution both in philosophy and in science.

  But Aristotle lived at the end of an era. Alexander the Great, whom he taught, died shortly before him, and so began the Hellenistic period of Greek history which saw a decline in Athens’ influence. The Roman Empire was becoming the dominant power in the Mediterranean, and the philosophy it adopted from Greece was that of the Stoics. The rival schools of Plato and Aristotle—Plato’s Academy and the Lyceum Aristotle founded in Athens—continued to operate, but they had lost their former eminence.

  As a result of this neglect, many of Aristotle’s writings were lost. It is believed that he wrote several hundred treatises and dialogues explaining his theories, but all that remain are fragments of his work, mainly in the form of lectures and teacher’s notes. Luckily for posterity, these were preserved by his followers, and there is enough contained in them to give a picture of the full range of his work.