Philosophy

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Philosophy is the discipline concerned with questions of how one should live (ethics); what sorts of things exist and what are their essential natures (metaphysics); what counts as genuine knowledge (epistemology); and what are the correct principles of reasoning (logic).^[1][2] The word is of Greek origin: φιλοσοφία (philosophía), a compound of φίλος (phílos: friend, or philia: lover) and σοφία (sophía: wisdom).^[3][4]

Though no single definition of philosophy is uncontroversial, and the field has historically expanded and changed depending upon what kinds of questions were interesting or relevant in a given era, it is generally agreed that philosophy is a method, rather than a set of claims, propositions, or theories. Its investigations are based upon rational thinking, striving to make no unexamined assumptions and no leaps based on faith or pure analogy. Different philosophers have had varied ideas about the nature of reason, and there is also disagreement about the subject matter of philosophy. Some think that philosophy examines the process of inquiry itself. Others, that there are essentially philosophical propositions which it is the task of philosophy to prove.^[5]

Until the Renaissance, 'philosophy' and 'science' were considered the same discipline.

Although the word "philosophy" originates in the Western tradition, many figures in the history of other cultures have addressed similar topics in similar ways.^[6] The philosophers of East Asia are discussed in Eastern philosophy, while the philosophers of North Africa and the Middle East, because of their strong interactions with Europe, are usually considered part of Western Philosophy.

Philosophical doctrines

Realism and nominalism

Main article: Realism

See also: Nominalism

Realism sometimes means the position opposed to the 18th-century Idealism, namely that some things have real existence outside the mind. Classically, however, realism is the doctrine that abstract entities corresponding to universal terms like 'man' have a real existence. It is opposed to nominalism, the view that abstract or universal terms are words only, or denote mental states such as ideas, beliefs, or intentions. The latter position, famously held by William of Ockham, is called 'conceptualism'.

Rationalism and empiricism

Main article: Rationalism

Main article: Empiricism

Rationalism is any view emphasizing the role or importance of human reason. Extreme rationalism tries to base all knowledge on reason alone. Rationalism typically starts from premises that cannot coherently be denied, then attempts by logical steps to deduce every possible object of knowledge.

The first rationalist, in this broad sense, is often held to be Parmenides (fl. 480 BCE), who argued that it is impossible to doubt that thinking actually occurs. But thinking must have an object, therefore something beyond thinking really exists. Parmenides deduced that what really exists must have certain properties – for example, that it cannot come into existence or cease to exist, that it is a coherent whole, that it remains the same eternally (in fact, exists altogether outside time). Zeno of Elea (born c. 489 BCE) was a disciple of Parmenides, and argued that motion is impossible, since the assertion that it exists implies a contradiction.

Plato (427–347 BCE) was also influenced by Parmenides, but combined rationalism with a form of realism. The philosopher's work is to consider being, and the essence of things. But the characteristic of essences is that they are universal. The nature of a man, a triangle, a tree, applies to all men, all triangles, all trees. Plato argued that these essences are mind-independent 'forms', that humans (but particularly philosophers) can come to know by reason, and by ignoring the distractions of sense-perception.

Modern rationalism begins with Descartes. Reflection on the nature of perceptual experience, as well as scientific discoveries in physiology and optics, led Descartes (and also Locke) to the view that we are directly aware of ideas, rather than objects. This view gave rise to three questions:

1. Is an idea a true copy of the real thing that it represents? Sensation is not a direct interaction between bodily objects and our sense, but is a physiological process involving representation (for example, an image on the retina). Locke thought that a 'secondary quality' such as a sensation of green could in no way resemble the arrangement of particles in matter that go to produce this sensation, although he thought that 'primary qualities' such as shape, size, number, were really in objects.
2. How can physical objects such as chairs and tables, or even physiological processes in the brain, give rise to mental items such as ideas? This is part of what became known as the mind-body problem.
3. If all we are aware of are our ideas, how can we know that anything else exists apart from ideas?

Descartes tried to address the last problem by reason. He began, echoing Parmenides, with a principle that he thought could not coherently be denied: I think, therefore I exist (often given in his original Latin: Cogito ergo sum). From this principle, Descartes went on to construct a complete system of knowledge (which involves proving the existence of God, using, among other means, a version of the ontological argument). His view that reason alone could yield substantial truths about reality strongly influenced those philosophers usually considered modern rationalists (such as Baruch Spinoza, Gottfried Leibniz, and Christian Wolff), while provoking criticism from other philosophers who have retrospectively come to be grouped together as empiricists.

Empiricism, in contrast to rationalism, downplays or dismisses the ability of reason alone to yield knowledge of the world, preferring to base any knowledge we have on our senses. John Locke propounded the classic empiricist view in An Essay Concerning Human Understanding in 1689, developing a form of naturalism and empiricism on roughly scientific (and Newtonian) principles.

During this era, religious ideas played a mixed role in the struggles that preoccupied secular philosophy. Bishop Berkeley's famous idealist refutation of key tenets of Isaac Newton is a case of an Enlightenment philosopher who drew substantially from religious ideas. Other influential religious thinkers of the time include Blaise Pascal, Joseph Butler, and Jonathan Edwards. Other major writers, such as Jean-Jacques Rousseau and Edmund Burke, took a rather different path. The restricted interests of many of the philosophers of the time foreshadow the separation and specialization of different areas of philosophy that would occur in the 20th century.

Skepticism

Main article: Skepticism

Skepticism is a philosophical attitude that questions the possibility of obtaining any sort of knowledge. It was first articulated by Pyrrho, who believed that everything could be doubted except appearances. Sextus Empiricus (1st century CE) describes skepticism as an "ability to place in antithesis, in any manner whatever, appearances and judgments, and thus [...] to come first of all to a suspension of judgment and then to mental tranquility."^[7] Skepticism so conceived is not merely the use of doubt, but is the use of doubt for a particular end: a calmness of the soul, or ataraxia. Skepticism poses itself as a challenge to dogmatism, whose adherents think they have found the truth.^[8]

Sextus noted that the reliability of perception may be questioned, because it is idiosyncratic to the perceiver. The appearance of individual things changes depending on whether they are in a group: for example, the shavings of a goat's horn are white when taken alone, yet the intact horn is black. A pencil, when viewed lengthwise, looks like a stick; but when examined at the tip, it looks merely like a circle.

Skepticism was revived in the early modern period by Michel de Montaigne and Blaise Pascal. Its most extreme exponent, however, was David Hume. Hume argued that there are only two kinds of reasoning: what he called probable and demonstrative (cf Hume's fork). Neither of these two forms of reasoning can lead us to a reasonable belief in the continued existence of an external world. Demonstrative reasoning cannot do this, because demonstration (that is, deductive reasoning from well-founded premises) alone cannot establish the uniformity of nature (as captured by scientific laws and principles, for example). Such reason alone cannot establish that the future will resemble the past. We have certain beliefs about the world (that the sun will rise tomorrow, for example), but these beliefs are the product of habit and custom, and do not depend on any sort of logical inferences from what is already given certain. But probable reasoning (inductive reasoning), which aims to take us from the observed to the unobserved, cannot do this either: it also depends on the uniformity of nature, and this supposed uniformity cannot be proved, without circularity, by any appeal to uniformity. The best that either sort of reasoning can accomplish is conditional truth: if certain assumptions are true, then certain conclusions follow. So nothing about the world can be established with certainty. Hume concludes that there is no solution to the skeptical argument – except, in effect, to ignore it.^[9]

Even if these matters were resolved in every case, we would have in turn to justify our standard of justification, leading to an infinite regress (hence the term regress skepticism).^[10][11]

Many philosophers have questioned the value of such skeptical arguments. The question of whether we can achieve knowledge of the external world is based on how high a standard we set for the justification of such knowledge. If our standard is absolute certainty, then we cannot progress beyond the existence of mental sensations. We cannot even deduce the existence of a coherent or continuing "I" that experiences these sensations, much less the existence of an external world. On the other hand, if our standard is too low, then we admit follies and illusions into our body of knowledge. This argument against absolute skepticism asserts that the practical philosopher must move beyond solipsism, and accept a standard for knowledge that is high but not absolute.

Idealism

Main article: Idealism

Idealism is the epistemological doctrine that nothing can be directly known outside of the minds of thinking beings. Or in an alternative stronger form, it is the metaphysical doctrine that nothing exists apart from minds and the "contents" of minds. In modern Western philosophy, the epistemological doctrine begins as a core tenet of Descartes – that what is in the mind is known more reliably than what is known through the senses. The first prominent modern Western idealist in the metaphysical sense was George Berkeley. Berkeley argued^[12] that there is no deep distinction between mental states, such as feeling pain, and the ideas about so-called "external" things, that appear to us through the senses. There is no real distinction, in this view, between certain sensations of heat and light that we experience, which lead us to believe in the external existence of a fire, and the fire itself. Those sensations are all there is to fire. Berkeley expressed this with the Latin formula esse est percipi: to be is to be perceived. In this view the opinion, "strangely prevailing upon men", that houses, mountains, and rivers have an existence independent of their perception by a thinking being is false.

Forms of idealism were prevalent in philosophy from the 18th century to the early 20th century. Transcendental idealism, advocated by Immanuel Kant, is the view that there are limits on what can be understood, since there is much that cannot be brought under the conditions of objective judgment. Kant wrote his Critique of Pure Reason (1781–1787) in an attempt to reconcile the conflicting approaches of rationalism and empiricism, and to establish a new groundwork for studying metaphysics. Kant's intention with this work was to look at what we know and then consider what must be true about it, as a logical consequence of, the way we know it. One major theme was that there are fundamental features of reality that escape our direct knowledge because of the natural limits of the human faculties.^[13] Although Kant held that objective knowledge of the world required the mind to impose a conceptual or categorical framework on the stream of pure sensory data – a framework including space and time themselves – he maintained that things-in-themselves existed independently of our perceptions and judgments; he was therefore not an idealist in any simple sense. Indeed, Kant's account of things-in-themselves is both controversial and highly complex. Continuing his work, Johann Gottlieb Fichte and Friedrich Schelling dispensed with belief in the independent existence of the world, and created a thoroughgoing idealist philosophy.

The most notable work of this German idealism was G.W.F. Hegel's Phenomenology of Spirit, of 1807. Hegel asserts that the twin aims of philosophy are to account for the contradictions apparent in human experience (which arise, for instance, out of the recognition of the self as both an active, subjective witness and a passive object in the world), and also simultaneously to resolve and preserve these contradictions by showing their compatibility at a higher level of examination. This program of acceptance and reconciliation of contradictions is known as the "Hegelian dialectic". Philosophers in the Hegelian tradition include Ludwig Andreas Feuerbach, Karl Marx, Friedrich Engels, and the British idealists, notably T.H. Green, J.M.E. McTaggart, and F.H. Bradley.

Few 20th century philosophers have embraced idealism. However, quite a few have embraced Hegelian dialectic. Immanuel Kant's "Copernican Turn" also remains an important philosophical concept today.

Pragmatism

Main article: Pragmatism

Main article: Instrumentalism

Pragmatism holds that the truth of beliefs does not consist in their correspondence with reality, but in their usefulness and efficacy.^[14] The late 19th-century American philosophers Charles Peirce and William James were its co-founders, and it was later developed by John Dewey as instrumentalism. Since the usefulness of any belief at any time might be contingent on circumstance, Peirce and James conceptualised final truth as that which would be established only by the future, final settlement of all opinion.^[15] Critics have accused pragmatism of falling victim to a simple fallacy: because something that is true proves useful, that usefulness is the basis for its truth.^[16] Thinkers in the pragmatist tradition have included John Dewey, George Santayana, and C.I. Lewis. Pragmatism has more recently been taken in new directions by Richard Rorty and Hilary Putnam.

Phenomenology

Main article: Phenomenology

Phenomenology, founded by Edmund Husserl, promotes the idea that the natural world is largely shaped by the human mind. An important part of Husserl's phenomenological project was to show that all conscious acts are directed at or about objective content, a feature that Husserl called intentionality.^[17]

Setting out to revise his views on the foundation of mathematics, and influenced by the philosopher and psychologist Franz Brentano, under whom he had studied in Vienna, Husserl began to lay the foundations for an ambitious account not just of the kinds of experiences that underlie and make possible mathematical judgments, but of the structure of conscious experience in general.^[18] In the first part of his two-volume work, the Logical Investigations (1901), he launched an extended attack on the psychologism of which he had been accused by Frege. In the second part, he began to develop the technique of descriptive phenomenology, with the aim of showing how objective judgments are indeed grounded in conscious experience – not, however, in the first-person experience of particular individuals, but in the properties essential to any experiences of the kind in question.^[19]

He also attempted to identify the essential properties of any act of meaning. He developed the method further in Ideas (1913) as transcendental phenomenology, proposing to ground actual experience, and thus all fields of human knowledge, in the structure of consciousness of an ideal, or transcendental, ego. Later, he attempted to reconcile his transcendental standpoint with an acknowledgement of the intersubjective life-world in which real individual subjects interact. Husserl published only a few works in his lifetime, which treat phenomenology mainly in abstract methodological terms; but he left an enormous quantity of unpublished concrete analyses.

Husserl's work was immediately influential in Germany, with the foundation of phenomenological schools in Munich and Göttingen. Phenomenology later achieved international fame through the work of such philosophers as Martin Heidegger (formerly Husserl's research assistant), Maurice Merleau-Ponty, and Jean-Paul Sartre. Indeed, through the work of Heidegger and Sartre, Husserl's focus on subjective experience influenced aspects of existentialism.

Existentialism

Main article: Existentialism

See also: Christian existentialism

Existentialism is a philosophical movement that rejects any predetermined role for human beings. Unlike tools, which are designed in order to fill some preconceived role (for example, a knife's preconceived role, or essence, is to cut), human beings are capable, to some extent at least, of deciding for themselves what constitutes their own essence.^[17] Although they didn't use the term, the 19th-century philosophers Søren Kierkegaard and Friedrich Nietzsche are widely regarded as the fathers of existentialism. Their influence, however, has extended beyond existentialist thought.^[20][21][22]

Two of the targets of Kierkegaard and Nietzsche's writings were the philosophical systems of Hegel and Schopenhauer respectively, which they had each admired in their youths. Kierkegaard thought Hegel ignored or excluded the inner subjective life of living human beings, while Nietzsche thought Schopenhauer's pessimism led people to live an ascetic, or self-hating, life. Kierkegaard suggested that truth is subjectivity, arguing that what is most important to a living individual are questions dealing with one's inner relationship to life.^[23][24] Nietzsche proposed perspectivism, which is the view that truth depends on individual perspectives.

Although Kierkegaard was among his influences, the extent to which the German philosopher Martin Heidegger should be considered an existentialist is debated. However, in Being and Time he presented a method of rooting philosophical explanations in human existence (Dasein) to be analysed in terms of existential categories (existentiale); and this has led many commentators to treat him as an important figure in the existentialist movement. In The Letter on Humanism, Heidegger explicitly rejected the existentialism of Jean-Paul Sartre.

Sartre became the best-known proponent of existentialism, exploring it not only in theoretical works such as Being and Nothingness , but also in plays and novels. Sartre, along with Albert Camus and Simone de Beauvoir, all represented an avowedly atheistic branch of existentialism, which is now more closely associated with their ideas of the novel nausea, contingency, bad faith, and the absurd than with Kierkegaard's spiritual angst. Nevertheless, the focus on the individual human being, responsible before the universe for the authenticity of his or her existence, is common to all these thinkers.

The analytic tradition

Main article: Analytic philosophy

The term analytic philosophy roughly designates a group of philosophical methods that stress clarity of meaning above all other criteria. The philosophy developed as a critique of Hegel and his followers in particular, and of speculative philosophy in general. Some schools in the group include 20th-century realism, logical atomism,