The history of philosophy is the study of philosophical ideas and concepts through time. Issues specifically related to history of philosophy might include (but are not limited to): How can changes in philosophy be accounted for historically? What drives the development of thought in its historical context? To what degree can philosophical texts from prior historical eras even be understood today?
All cultures — be they prehistoric, ancient, mediæval, or modern; Eastern, Western, religious or secular — have had their own unique schools of philosophy, arrived at through both inheritance and through independent discovery. Such theories have grown from different premises and approaches, examples of which include (but are not limited to) rationalism (theories arrived at through logic), empiricism (theories arrived at through observation), and even through leaps of faith, hope and inheritance (such as the supernaturalist philosophies and religions).
History of philosophy seeks to catalogue and classify such development. The goal is to understand the development of philosophical ideas through time.
Western philosophy has a long history, conventionally divided into four large eras - the Ancient, Medieval, Modern and Contemporary. The Ancient era runs through the fall of Rome and includes the Greek philosophers such as Plato. The Medieval period runs until roughly the late 1400s and the Renaissance. The "Modern" is a word with more varied use, which includes everything from Post-Medieval through the specific period up to the 20th century. Contemporary philosophy encompasses the philosophical developments of the 20th century up to the present day.
Western Philosophy is generally said to begin in the Greek cities of western Asia Minor (Ionia) with Thales of Miletus, who was active around 585 B.C. and left us the opaque dictum, "all is water." His most noted students were Anaximenes of Miletus ("all is air") and Anaximander.
Other thinkers and schools appeared throughout Greece over the next couple of centuries. Among the most important were Heraclitus ("all is fire", all is chaotic and transitory), Anaxagoras (reality is so ordered that it must be in all respects governed by mind), the Pluralists and Atomists (the world is composite of innumerable interacting parts), the Eleatics Parmenides and Zeno (all is One and change is impossible), the Sophists (became known, perhaps unjustly, for claiming that truth was no more than opinion and for teaching people to argue fallaciously to prove whatever conclusions they wished). This whole movement gradually became more concentrated in Athens, which had become the dominant city-state in Greece.
There is considerable discussion about why Athenian culture encouraged philosophy, but a popular theory says that it occurred because Athens had a direct democracy. It is known from Plato's writings that many sophists maintained schools of debate, were respected members of society, and were well paid by their students. Orators influenced Athenian history, possibly even causing its failure (See Battle of Lade). Another theory explains the birth of philosophical debate in Athens with the presence of a slave labor workforce which performed the necessary functions that would otherwise have consumed the time of the free male citizenry. Freed from working in the fields or other manual economic activities, they were able to participate in the assemblies of Athens and spend long periods in discussions on popular philosophical questions. Students of Sophists needed to acquire the skills of oration in order to influence the Athenian Assembly and thereby increase respect and wealth. In response, the subjects and methods of debate became highly developed by the Sophists.
The key figure in transforming Greek philosophy into a unified and continuous project - the one still being pursued today - is Socrates, who studied under several Sophists. It is said that following a visit to the Oracle of Delphi he spent much of his life questioning anyone in Athens who would engage him, in order to disprove the oracular prophecy that there would be no man wiser than Socrates. Through these live dialogues, he examined common but critical concepts that lacked clear or concrete definitions, such as beauty and truth, and the virtues of piety, wisdom, temperance, courage, and justice. Socrates' awareness of his own ignorance allowed him to discover his errors as well as the errors of those who claimed knowledge based upon falsifiable or unclear precepts and beliefs. He wrote nothing, but inspired many disciples, including many sons of prominent Athenian citizens (including Plato), which led to his trial and execution in 399 B.C. on the charge that his philosophy and sophistry were undermining the youth, piety, and moral fiber of the city. He was offered a chance to flee from his fate but chose to remain in Athens, abide by his principles, and drink the poison hemlock.
Socrates' most important student was Plato, who founded the Academy of Athens and wrote a number of dialogues, which applied the Socratic method of inquiry to examine philosophical problems. Some central ideas of Plato's dialogues are the Theory of Forms, i.e., that the mind is imbued with an innate capacity to understand and contemplate concepts from a higher order preeminent world, concepts more real, permanent, and universal than or representative of the things of this world, which are only changing and temporal; the idea of the immortal soul being superior to the body; the idea of evil as simple ignorance of truth; that true knowledge leads to true virtue; that art is subordinate to moral purpose; and that the society of the city-state should be governed by a merit class of propertyless philosopher kings, with no permanent wives or paternity rights over their children, and be protected by an athletically gifted, honorable, duty bound military class. In the later dialogues Socrates figures less prominently, but Plato had previously woven his own thoughts into some of Socrates' words. Interestingly, in his most famous work, The Republic, Plato critiques democracy, condemns tyranny, and proposes a three tiered merit based structure of society, with workers, guardians and philosophers, in an equal relationship, where no innocents would ever be put to death again, citing the philosophers' relentless love of truth and knowledge of the forms or ideals, concern for general welfare and lack of propertied interest as causes for their being suited to govern.
Plato's most outstanding student was Aristotle, perhaps the first truly systematic philosopher. Aristotelian logic was the first type of logic to attempt to categorize every valid syllogism. A syllogism is a form of argument that is guaranteed to be accepted, because it is known (by all educated persons) to be valid. A crucial assumption in Aristotelian logic is that it has to be about real objects. Two of Aristotle's syllogisms are invalid to modern eyes. For example, "All A are B. All A are C. Therefore, some B are C." This syllogism fails if set A is empty, but there are real members of set B. In Aristotle's syllogistic logic you could say this, because his logic should only be used for things that really exist ("no empty classes")
The application of Aristotelian logic is preceded by having the student memorize a rather large set of syllogisms. The memorization proceeded from diagrams, or learning a key sentence, with the first letter of each word reminding the student of the names of the syllogisms.
Each syllogism had a name, for example: "Modus Ponens" had the form of "If A is true, then B is true. A is true, therefore B is true."
Most university students of logic memorized Aristotle's 19 syllogisms of two subjects, permitting them to validly connect a subject and object. A few geniuses developed systems with three subjects, or described a way of elaborating the rules of three subjects.
If God exists at all, surely He is the most important feature of the universe, and therefore worthy of study. One continuing interest in this time was to prove the existence of God, through logic alone, if possible.
One early effort was the cosmological argument, conventionally attributed to Thomas Aquinas. The argument roughly is that everything that exists has a cause. But there could not be an infinite chain of causes back into the past, there must have been an uncaused "first cause." This is God. Aquinas also adapted this argument to prove the goodness of God. Everything has some goodness, and the cause of each thing is better than the thing caused. Therefore, the first cause is the best possible thing. Similar arguments are used to prove God's power and uniqueness.
Another important argument for proof of the existence of God was the ontological argument, advanced by St. Anselm. Basically, it says that God has all possible good features. Existence is good, and therefore God has it, and therefore exists. This argument has been used in different forms by philosophers from Descartes forward.
The definition of the word "philosophy" in English has changed over the centuries -- in medieval times, any research outside the fields of theology or medicine was called "philosophy", hence the Philosophical Transactions of the Royal Society is a scientific journal dating from 1665, the Doctor of Philosophy (Ph.D.) degree covers a wide range of subjects, and the Cambridge Philosophical Society is actually concerned with what we would now call science and not modern philosophy.
As with many periodizations, there are multiple current usages for the term "Modern Philosophy" that exist in practice. One usage is to date modern philosophy from the "Age of Reason", where systematic philosophy became common, excluding Erasmus and Machiavelli as "modern philosophers". Another is to date it, the way the entire larger modern period is dated, from the Renaissance. In some usages, "Modern Philosophy" ended in 1800, with the rise of Hegelianism and Idealism. There is also the lumpers/splitters problem, namely that some works split philosophy into more periods than others: one author might feel a strong need to differentiate between "The Age of Reason" or "Early Modern Philosophers" and "The Enlightenment", another author might write from the perspective that 1600-1800 is essentially one continuous evolution, and therefore a single period. Wikipedia's philosophy section therefore hews more closely to centuries as a means of avoiding long discussions over periods, but it is important to note the variety of practice that occurs.
A broad overview would then have Erasmus, Francis Bacon, Niccolò Machiavelli, and Galileo Galilei represent the rise of empiricism and humanism in place of scholastic tradition. 17th-century philosophy is dominated by the need to organize philosophy on rational, skeptical, logical and axiomatic grounds, such as the work of René Descartes, Blaise Pascal, and Thomas Hobbes. This type of philosophy attempts to integrate religious belief into philosophical frameworks, and, often to combat atheism or other unbeliefs, by adopting the idea of material reality, and the dualism between spirit and material. The extension, and reaction, against this would be the monism of George Berkeley (idealism) and Benedict de Spinoza (dual aspect theory). It was during this time period that the empiricism was developed as an alternative to skepticism by John Locke, George Berkeley and others. It should be mentioned that John Locke, Thomas Hobbes and Edmund Burke developed their well known political philosophies during this time, as well.
The 18th-century philosophy article deals with the period often called the early part of "The Enlightenment" in the shorter form of the word, and centers on the rise of systematic empiricism, following after Sir Isaac Newton's natural philosophy. Thus Diderot, Voltaire, Rousseau, Montesquieu, Kant and the political philosophies embodied by and influencing the American Revolution are part of The Enlightenment. Other prominent philosophers of this time period were David Hume and Adam Smith, who, along with Francis Hutcheson, were also the primary philosophers of the Scottish Enlightenment.
The 19th century took the radical notions of self-organization and intrinsic order from Goethe and Kantian metaphysics, and proceeded to produce a long elaboration on the tension between systematization and organic development. Foremost was the work of Hegel, whose Logic and Phenomenology of Spirit produced a "dialectical" framework for ordering of knowledge. The 19th century would also include Schopenhauer's negation of the will. As with the 18th century, it would be developments in science that would arise from, and then challenge, philosophy: most importantly the work of Charles Darwin, which was based on the idea of organic self-regulation found in philosophers such as Adam Smith, but fundamentally challenged established conceptions.
The 20th century deals with the upheavals produced by a series of conflicts within philosophical discourse over the basis of knowledge, with classical certainties overthrown, and new social, economic, scientific and logical problems. 20th century philosophy was set for a series of attempts to reform and preserve, and to alter or abolish, older knowledge systems. Seminal figures include Sigmund Freud, Friedrich Nietszche, Ernst Mach, John Dewey. Epistemology (theory of knowledge) and its basis was a central concern, as seen from the work of Heidegger, Karl Popper, Claude Lévi-Strauss and Bertrand Russell. Phenomenologically oriented metaphysics undergirded existentialism (Jean-Paul Sartre, Søren Kierkegaard, Albert Camus) and finally poststructuralism (Gilles Deleuze, Jean-François Lyotard, Michel Foucault, Jacques Derrida). Also notable was the rise of "pop" philosophers who promulgated systems for dealing with the world but were isolated philosophically, including Ayn Rand. Conversely, some philosophers have attempted to define and rehabilitate older traditions of philosophy. Most notably, Hans-Georg Gadamer and Alasdair MacIntyre have both, albeit in different ways, revived the tradition of Aristotelianism.
In the West, the term Eastern philosophy refers very broadly to the various philosophies of "the East," namely Asia, including China, India, Japan, Persia and the general area. One must take into account that this term ignores that these countries do not belong to a single culture.
Ancient eastern philosophy developed mainly in India and China. The Indian or Hindu schools of philosophy can be considered the oldest schools of philosophy - they predate Greek philosophy by almost 500 years. Hindu philosophy primarily begins with Upanishads, which can be dated close to 800 BC. The oldest, such as the Brhadaranyaka and Chandogya Upanishads, have been dated to around the eighth century BCE. The philosophical edifice of Indian religions viz., Hinduism, Jainism, Buddhism is built on the foundation laid by the Upanishads. Hindu philosophy is followed by the Buddhist and Jain philosophies. Confucianism can be considered as the oldest school of philosophy in China. Confucianism developed in China around the same time as Buddhism and Jainism developed in India. Another school of philosophy, Taoism, developed in China around 200 BC.
Abrahamic philosophy, in its loosest sense, comprises the series of philosophical schools that emerged from the study and commentary of the common ancient Semitic tradition which can be traced by their adherents to Abraham ("Father/Leader of many" Hebrew אַבְרָהָם ("Avraham") Arabic ابراهيم ("Ibrahim"), a patriarch whose life is narrated in the Hebrew Bible/Old Testament, and as a prophet in the Qur'an and also called a prophet in Genesis 20:7.
The standard text common to all of these subsequent traditions are what is known as the Hebrew Bible, roughly the first five books of the Old Testament, starting with the book of Genesis through to Deuteronomy. However, each of them added substantially different texts to their emerging canons, and hence their respective philosophical developments varied widely.
- The history of religious and philosophical ideas, in Dictionary of the History of Ideas
- Evil in Modern Thought: An Alternative History of Philosophy. A documentary film about the problem of evil.