Philosophy

The practice of philosophy is characterized by various general features: it is a form of rational inquiry, it aims to be systematic, and it tends to critically reflect on its own methods and presuppositions.[16] It requires thinking "as hard and as clearly...about some of the most interesting and enduring problems that human minds have ever encountered".[17]

According to the 18th-century philosopher Immanuel Kant, the task of philosophy is united by four questions: "What can I know?"; "What should I do?"; "What may I hope?"; and "What is the human being?" His entire career, as he conceived it, was devoted to systematically addressing these four questions.[18][19][20]

The theme of self-critical intellectual humility may be traced back to the origins of Western philosophy. Socrates, as depicted in Plato's dialogues, famously expresses incredulity when told by the Oracle at Delphi that he was the wisest person of all. What he comes to conclude is that his wisdom consists in his knowing that he does not possess the most exalted kind of wisdom, namely, that about what is truly fine and good.[21][22] Consistent with his well-known assertion that "the unexamined life is not worth living", Socrates arrives at the conclusion that the active pursuit of wisdom is good and valuable in itself, irrespective of whether one ever arrives at final definitions.[23][24] This is consistent with the view that the kind of knowledge that philosophy seeks is not information, but understanding.[25]

Confronting the unlikelihood of ever arriving at final answers to the great questions of philosophy, Bertrand Russell offers this justification for nevertheless undertaking the labor: "The man who has no tincture of philosophy goes through life imprisoned in the prejudices derived from common sense, from the habitual beliefs of his age or his nation, and from convictions which have grown up in his mind without the cooperation or consent of his deliberate reason."[26][27] This passage has been cited to advance an interpretation of philosophy as "freeing us from prejudice, self-deceptive notions, and half-truths".[28]

Attempts to define philosophy in precise terms are controversial[29][14] and are studied in the subdiscipline known as metaphilosophy.[30] Some approaches argue that there is a set of essential features shared by all parts of philosophy. Others see only weaker family resemblances or contend that it is merely an empty blanket term.[31][32][33] Precise definitions are often only accepted by theorists belonging to a certain philosophical movement and are revisionistic according to Søren Overgaard et al. in that many presumed parts of philosophy would not deserve the title "philosophy" if they were true.[34][35]

Some definitions characterize philosophy in relation to its method, like pure reasoning. Others focus on its topic, for example, as the study of the biggest patterns of the world as a whole or as the attempt to answer the big questions.[36][37][38] Both approaches have the problem that they are usually either too wide, by including non-philosophical disciplines, or too narrow, by excluding some philosophical sub-disciplines.[36]

Many definitions of philosophy emphasize its intimate relation to science.[14] In this sense, philosophy is sometimes understood as a proper science in its own right. According to some naturalistic philosophers, like W. V. O. Quine, philosophy is an empirical yet abstract science that is concerned with wide-ranging empirical patterns instead of particular observations.[39][40] Science-based definitions usually face the problem of explaining why philosophy in its long history has not made the type of progress seen in other sciences.[41][42][43] This problem is avoided by seeing philosophy as an immature or provisional science whose subdisciplines cease to be philosophy once they have fully developed.[14][32][44] In this sense, philosophy is sometimes described as "the midwife of the sciences".[45][14]

Other definitions focus on the contrast between science and philosophy. A common theme among many such conceptions is that philosophy is concerned with meaning, understanding, or the clarification of language.[46][47] According to one view, philosophy is conceptual analysis, which involves finding the necessary and sufficient conditions for the application of concepts.[48][38][49]

Phenomenologists, such as Edmund Husserl, characterize philosophy as a "rigorous science" investigating essences.[50] They practice a radical suspension of theoretical assumptions about reality in order to get back to the "things themselves", that is, as originally given in experience. They contend that this base-level of experience provides the foundation for higher-order theoretical knowledge, and that one needs to understand the former in order to understand the latter.[51]

Another approach presents philosophy as a linguistic therapy. According to Ludwig Wittgenstein, for example, philosophy aims at dispelling misunderstandings to which humans are susceptible due to the confusing structure of natural language.[14][52][53]

An early approach found in ancient Greek and Roman philosophy, and later adopted by 20th-century philosophers such as Michel Foucault and Pierre Hadot, is that philosophy is the spiritual practice of developing one's rational capacities.[54][55] This practice is an expression of the philosopher's love of wisdom and has the aim of improving one's well-being by leading a reflective life.[56]

Another definition characterizes philosophy as thinking about thinking. This emphasizes its self-critical, reflective nature.[57][58]

Statue of Aristotle, a major figure of ancient Greek philosophy, in Aristotle's Park, Stagira

Western philosophy originated in Ancient Greece in the 6th century BCE with the Presocratics. They attempted to provide rational explanations of the cosmos as a whole.[65][66][67] The philosophy following them was shaped by Socrates (469–399 BCE), Plato (427–347 BCE), and Aristotle (384–322 BCE). They expanded the range of topics to questions like how people should act, how to arrive at knowledge, and what the nature of reality and mind is.[68][69] The later part of the ancient period was marked by the emergence of philosophical movements like Epicureanism, Stoicism, Skepticism, and Neoplatonism.[70][71][72] The medieval period started in the 5th century CE. Its focus was on religious topics and many thinkers used ancient philosophy to explain and further elaborate Christian doctrines.[73][74][75]

The Renaissance period started in the 14th century and saw a renewed interest in various schools of Ancient philosophy, in particular Platonism. Humanism also emerged in this period.[76] The modern period started in the 17th century. One of its central concerns was how philosophical and scientific knowledge are created. Specific importance was given to the role of reason and sensory experience.[77][78] Many of these innovations were used in the Enlightenment movement to challenge traditional authorities.[79][80] Various attempts to develop all-inclusive systems of philosophy were made in the 19th century, for example, by German idealism.[81] Influential developments in 20th-century philosophy were the emergence and application of formal logic and the focus on the role of language as well as pragmatism and movements in continental philosophy like phenomenology, existentialism, and postmodernism.[82][83] The 20th century saw a rapid expansion of academic philosophy in terms of the number of philosophical publications and philosophers working at academic institutions.[82] There was also a noticeable growth in the number of female philosophers, but they still remained underrepresented.[84]

Arabic-Persian philosophy arose in the early 9th century CE as a response to discussions in the Islamic theological tradition. Its classical period lasted until the 12th century CE and was strongly influenced by Ancient Greek philosophers. It employed their ideas to elaborate and interpret the teachings of the Quran.[85]

An Iranian portrait of Avicenna on a Silver Vase. He was one of the most influential philosophers of the Islamic Golden Age.

Al-Kindi (801–873 CE) is usually regarded as the first philosopher of this tradition. He translated and interpreted many works of Aristotle and Neoplatonists in his attempt to show that there is a harmony between reason and faith.[86] Avicenna (980–1037 CE) also followed this goal and developed a comprehensive philosophical system to provide a rational understanding of reality encompassing science, religion, and mysticism.[87][88] Al-Ghazali (1058–1111 CE) was a strong critic of the idea that reason can arrive at a true understanding of reality and God. He formulated a detailed critique of philosophy and tried to assign philosophy a more limited place besides the teachings of the Quran and mystical insight.[89] Following Al-Ghazali and the end of the classical period, the influence of philosophical inquiry waned.[90][91] Mulla Sadra (1571–1636 CE) is often regarded as one of the most influential philosophers of the subsequent period.[92][93] The increasing influence of Western thought and institutions in the 19th and 20th centuries gave rise to the intellectual movement of Islamic modernism, which aims to understand the relation between traditional Islamic beliefs and modernity. [94][95][96]

One of the distinguishing features of Indian philosophy is that it integrates the exploration of the nature of reality, the ways of arriving at knowledge, and the spiritual question of how to reach enlightenment.[97][98] It started around 900 BCE when the Vedas were written. They are the foundational scriptures of Hinduism and contemplate issues concerning the relation between the self and ultimate reality as well as the question of how souls are reborn based on their past actions.[99] This period also saw the emergence of non-Vedic teachings, like Buddhism and Jainism.[100][101] Buddhism was founded by Gautama Siddhartha (563–483 BCE), who challenged the Vedic idea of a permanent self and proposed a path to liberate oneself from suffering.[100][101] Jainism was founded by Mahavira (599–527 BCE), who emphasized non-violence as well as respect toward all forms of life.[100][102][103]

The subsequent classical period started roughly 200 BCE and was characterized by the emergence of the six orthodox schools of Hinduism: Nyāyá, Vaiśeṣika, Sāṃkhya, Yoga, Mīmāṃsā, and Vedanta.[104][105][106] The school of Advaita Vedanta developed later in this period. It was systematized by Adi Shankara (c.700–750 CE), who held that everything is one and that the impression of a universe consisting of many distinct entities is an illusion.[107][108][109] A slightly different perspective was defended by Ramanuja (1017–1137 CE)[lower-alpha 1], who founded the school of Vishishtadvaita Vedanta and argued that individual entities are real as aspects or parts of the underlying unity.[111] He also helped to popularize the Bhakti movement, which taught devotion toward the divine as a spiritual path and lasted until the 17th to 18th centuries CE.[112] The modern period began roughly 1800 CE and was shaped by the encounter with Western thought.[113][114] Various philosophers tried to formulate comprehensive systems to harmonize diverse philosophical and religious teachings. For example, Swami Vivekananda (1863–1902 CE) used the teachings of Advaita Vedanta to argue that all the different religions are valid paths toward the one divine.[115]

The teachings of Confucius on ethics and society shaped subsequent Chinese philosophy.

Chinese philosophy is particularly interested in practical questions associated with right social conduct, government, and self-cultivation.[116] In competing attempts to resolve the politically turbulent 6th century BCE, many schools of thought emerged. The most prominent among them were Confucianism and Daoism.[117][118] Confucianism was founded by Confucius (551–479 BCE). It focused on different forms of moral virtues and explored how they lead to harmony in society.[119] Daoism was founded by Laozi (6th century BCE) and examined how humans can live in harmony with nature by following the Dao or the natural order of the universe.[120] Other influential early schools of thought were Mohism, which developed an early form of altruistic consequentialism,[121][122][123] and Legalism, which emphasized the importance of a strong state and strict laws.[121][124][125]

Buddhism was introduced to China in the 1st century CE and produced new forms of Buddhism.[126][127] Starting in the 3rd century CE, the school of Xuanxue emerged. It interpreted earlier Daoist works with a specific emphasis on metaphysical explanations.[126][127] Neo-Confucianism developed in the 11th century CE. It systematized previous Confucian teachings and sought a metaphysical foundation of ethics.[128][127] The modern period in Chinese philosophy began in the early 20th century and was shaped by the influence of and reactions to Western philosophy. The emergence of Chinese Marxism—which focused on class struggle, socialism, and communism—resulted in a significant transformation of the political landscape.[129] Another development was the emergence of New Confucianism, which aims to modernize and rethink Confucian teachings to explore their compatibility with democratic ideals and modern science.[130][131][132]

Epistemology is the branch of philosophy that studies knowledge. It is also known as theory of knowledge and aims to understand what knowledge is, how it arises, what its limits are, and what value it has. It further examines the nature of truth, belief, justification, and rationality.[139] Some of the questions addressed by epistemologists include "By what method(s) can one acquire knowledge?"; "How is truth established?"; and "Can we prove causal relations?"[140]

Epistemology is primarily interested in declarative knowledge or knowledge of facts, like knowing that Princess Diana died in 1997. But it also investigates practical knowledge, like knowing how to ride a bicycle, and knowledge by acquaintance, like knowing a celebrity personally.[141][142][143]

One area in epistemology is the analysis of knowledge. It assumes that declarative knowledge is a combination of different parts and attempts to identify what those parts are. An influential theory in this area claims that knowledge has three components: it is a belief that is justified and true. This theory is controversial and the difficulties associated with it are known as the Gettier problem.[144][145]

Another area in epistemology asks how people acquire knowledge. Often-discussed sources of knowledge are perception, introspection, memory, inference, and testimony.[146][147] According to empiricists, all knowledge is based on some form of experience. Rationalists reject this view and hold that some forms of knowledge, like innate knowledge, are not acquired through experience.[148][149][150] The regress problem is a common issue in relation to the sources of knowledge and the justification they offer. It is based on the idea that beliefs require some kind of reason or evidence to be justified. The problem is that the source of justification may itself be in need of another source of justification. This leads to an infinite regress or circular reasoning. This idea is rejected by foundationalists, who argue that some sources can provide justification without requiring justification themselves.[151][152] Another solution is presented by coherentists, who state that a belief is justified if it coheres with other beliefs of the person.[153]

Many discussions in epistemology touch on the topic of philosophical skepticism, which raises doubts about some or all claims to knowledge. These doubts are often based on the idea that knowledge requires absolute certainty and that humans are unable to acquire it.[154][155][156]

"The utilitarian doctrine is, that happiness is desirable, and the only thing desirable, as an end; all other things being only desirable as means to that end." — John Stuart Mill, Utilitarianism (1863)[157]

Ethics, also known as moral philosophy, studies what constitutes right conduct. It is also concerned with the moral evaluation of character traits and institutions. It explores what the standards of morality are and how to live a good life.[158][159][160] Philosophical ethics addresses such basic questions as "Are moral obligations relative?"; "Which has priority: well-being or obligation?"; and "What gives life meaning?"[161]

The main branches of ethics are meta-ethics, normative ethics, and applied ethics. Meta-ethics asks abstract questions about the nature and sources of morality. It analyzes the meaning of ethical concepts, like right action and obligation. It also investigates whether ethical theories can be true in an absolute sense and how to acquire knowledge of them. Normative ethics encompasses general theories of how to distinguish between right and wrong conduct. It helps guide moral decisions by examining what moral obligations and rights people have. Applied ethics studies the consequences of the general theories developed by normative ethics in specific situations, for example, in the workplace or for medical treatments.[162]

Within contemporary normative ethics, consequentialism, deontology, and virtue ethics are influential schools of thought.[163][164] Consequentialists judge actions based on their consequences. One such view is utilitarianism, which argues that actions should increase overall happiness while minimizing suffering. Deontologists judge actions based on whether they follow moral duties, like abstaining from lying or killing. According to them, what matters is that actions are in tune with those duties and not what consequences they have. Virtue theorists judge actions based on the moral character of the agent who performs them. According to this view, actions should conform to what an ideally virtuous agent would do by manifesting virtues like generosity and honesty.[163][164][165]

Logic is the study of correct reasoning. It aims to understand how to distinguish good from bad arguments.[166][167] It is usually divided into formal and informal logic. Formal logic uses artificial languages with a precise symbolic representation to investigate arguments. In this way, it formulates exact criteria and methods based on the structure of arguments to determine whether they are correct or incorrect. Informal logic uses non-formal criteria and standards to analyze and evaluate the correctness of arguments. It relies on additional factors such as content and context.[168]

Logic examines a variety of arguments. Deductive arguments are mainly studied by formal logic. An argument is deductively valid if the truth of its premises ensures the truth of its conclusion. Deductively valid arguments follow a rule of inference, like modus ponens, which has the following logical form: "p; if p then q; therefore q". An example is the argument "today is Sunday; if today is Sunday then I don't have to go to work today; therefore I don't have to go to work today".[169][170][171]

The premises of non-deductive arguments also support their conclusion. However, this support is not as certain and does not guarantee that the conclusion is true.[172][173] One form is inductive reasoning. It starts from a set of individual cases and uses generalization to arrive at a universal law governing all cases. An example is the inference that "all ravens are black" based on observations of many individual black ravens.[174][175][176] Another form is abductive reasoning. It starts from an observation and concludes that the best explanation of this observation must be true. This happens, for example, when a doctor diagnoses a disease based on the observed symptoms.[177][178][175]

Logic also investigates incorrect forms of reasoning. They are called fallacies and are divided into formal and informal fallacies based on whether the source of the error lies only in the form of the argument or also in its content and context.[179]

The beginning of Aristotle's Metaphysics in an incunabulum decorated with hand-painted miniatures

Metaphysics is the study of the most general features of reality, such as existence, objects and their properties, wholes and their parts, space and time, events, and causation.[180][181][182] There are disagreements about the precise definition of the term and its meaning has changed throughout the ages.[183] Metaphysicists attempt to answer basic questions like "Why is there something rather than nothing?"; "Of what does reality ultimately consist?"; and "Are humans free?"[184]

Metaphysics is sometimes divided into general metaphysics and specific or special metaphysics. General metaphysics investigates being as such. It examines the features that all entities have in common. Specific metaphysics is interested in different kinds of being, the features they have, and how they differ from one another.[180][181][185]

An important area in metaphysics is ontology. Some theorists identify it with general metaphysics. Ontology investigates concepts like being, becoming, and reality. It studies the categories of being and asks what exists on the most fundamental level.[186] Another subfield of metaphysics is philosophical cosmology. It is interested in the essence of the world as a whole. It asks questions like whether the universe has a beginning and an end and whether it was created by something else.[182][187]

A key topic in metaphysics concerns the question of whether reality only consists of physical things like matter and energy. Alternative suggestions are that mental entities (like souls and experiences) and abstract entities (like numbers) exist apart from physical things. Another topic in metaphysics concerns the problem of identity. It asks questions like how much an entity can change while still remaining the same entity.[182] According to one view, entities have essential and accidental features. They can change their accidental features but they cease to be the same entity if they lose an essential feature.[188][189] A central distinction in metaphysics is between particulars and universals. Universals, like the color red, can exist at different locations at the same time. This is not the case for particulars, like individual persons or specific objects.[190][191] Other metaphysical questions are whether the past fully determines the present and what implications this would have for the existence of free will.[192][193]

There are many additional subfields of philosophy besides its core branches. Some of the most prominent are aesthetics, philosophy of language, philosophy of mind, philosophy of religion, philosophy of science, and political philosophy.[194]

Aesthetics in the philosophical sense is the field that studies the nature and appreciation of beauty and other aesthetic properties, like the sublime.[195] Although it is often treated together with the philosophy of art, aesthetics is a broader category that encompasses other aspects of experience, such as natural beauty.[196][197] In a more general sense, aesthetics is the "critical reflection on art, culture, and nature".[198][199] A key question in aesthetics is whether beauty is an objective or mind-independent feature of entities. This view is rejected by subjectivists, who claim that beauty is not an inherent quality of objects, but depends on how people subjectively experience them.[197][200] Aesthetic philosophers also investigate the nature of aesthetic experiences and judgments. Further topics include the essence of works of art and the processes involved in creating them.[201][197]

The philosophy of language studies the nature and function of language. It examines the concepts of meaning, reference, and truth. It aims to answer questions like how words are related to things and how language affects human thought and understanding. It is closely related to the disciplines of logic and linguistics.[202][203][204] The philosophy of language rose to particular prominence in the early 20th century in analytic philosophy due to the works of Frege and Russell. One of its central topics is to understand how sentences get their meaning. There are two broad theoretical camps: those emphasizing the formal truth conditions of sentences[lower-alpha 2] and those investigating circumstances that determine when it is suitable to use a sentence, the latter of which is associated with speech act theory.[206][207]

The philosophy of mind studies the nature of mental phenomena and how they are related to the physical world.[208][209] It aims to understand different types of conscious and unconscious mental states, like beliefs, desires, intentions, feelings, sensations, and free will.[210][211] An influential intuition in the philosophy of mind is the distinction between an inner world of experience of an object and the existence of this object in the outer world. The mind-body problem is the problem of explaining how matter and mind are related. The main traditional responses are materialism, which assumes that matter is more fundamental; idealism, which assumes that mind is more fundamental; and dualism, which assumes that mind and matter are distinct types of entities. In contemporary philosophy, a widely accepted position is functionalism, which understands mental states in terms of the functional or causal roles they play.[212] The mind-body problem is closely related to the hard problem of consciousness, which asks how the physical brain can produce qualitatively subjective experiences.[213][214]

The philosophy of religion investigates the basic concepts, assumptions, and arguments associated with religion. It critically reflects on what religion is, how to define the divine, and whether one or more gods exist. It also includes the discussion of worldviews that reject religious doctrines.[215] Further questions addressed by the philosophy of religion are: "How are we to interpret religious language, if not literally?";[216] "Is divine omniscience compatible with free will?";[217] and, "Are the great variety of world religions in some way compatible in spite of their apparently contradictory theological claims?"[218] It includes topics from nearly all branches of philosophy.[219][220] It differs from theology since theological debates typically take place within one religious tradition, while debates in the philosophy of religion transcend any particular set of theological assumptions.[221][222]

The philosophy of science examines the fundamental concepts, assumptions, and problems associated with science. It reflects on what science is and how to distinguish it from pseudoscience. It investigates the methods employed by scientists, how their application can result in knowledge, and on what assumptions they are based. It also studies the purpose and implications of science.[223] Some of its questions are "What counts as an adequate explanation?";[224] "Is a scientific law anything more than a description of a regularity?";[225] and "Can some special sciences be explained entirely in the terms of a more general science?"[226] It is a vast field that is commonly divided into the philosophy of the natural sciences and the philosophy of the social sciences, with further subdivisions for each of the individual sciences under these headings. How these branches are related to one another is also a question in the philosophy of science. Many of its philosophical issues overlap with the fields of metaphysics or epistemology.[227][228]

Political philosophy is the philosophical inquiry into the fundamental principles and ideas governing political systems and societies. It examines the basic concepts, assumptions, and arguments in the field of politics. It investigates the nature and purpose of government and compares its different forms.[229] It further asks under what circumstances the use of political power is legitimate, rather than a form of simple violence.[230][231] In this regard, it is concerned with the distribution of political power, social and material goods, as well as legal rights.[232] Other topics are justice, liberty, equality, sovereignty, and nationalism.[230] Political philosophy involves a general inquiry into normative matters and differs in this respect from political science, which aims to provide empirical descriptions of actually existing states.[233][230] Political philosophy is often treated as a subfield of ethics.[234] Influential schools of thought in political philosophy are liberalism, conservativism, socialism, and anarchism.[235][236]