Reason

• 1. Introduction

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  Reason is the capacity to consciously apply logic, drawing valid conclusions from new or existing information with the aim of seeking truth. Aristotle defined human beings as rational animals, and across centuries philosophers have treated this faculty as the thing that sets people apart. The source ties reason to philosophy, religion, science, language, and mathematics, the activities considered characteristic of humans.

  Yet the word itself carries a tangled inheritance. It descends from the Greek logos and the Latin ratio, terms that once also meant an account of money handled. Why would the highest faculty of the human mind share a root with bookkeeping? And if reason is what makes us human, what happens when a thinker insists it is, in Hume's words, only ever the slave of the passions?

  This documentary follows reason through its quarrels. It asks whether the cosmos itself once reasoned, whether animals can reason, whether faith and reason can share a roof, and whether a life guided by reason actually leads to greater happiness than any other.

• 2. Logos And Ratio

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  The original Greek term was logos, the root of the modern English word logic. But logos could also mean speech, or explanation, or an account of money handled. When it crossed into Latin in its non-linguistic senses, it became ratio, a word that likewise served as a translation for logos in the sense of a financial account.

  French raison descends directly from Latin, and from raison comes the English word reason. The earliest major philosophers to publish in English routinely wrote in Latin and French too, including Francis Bacon, Thomas Hobbes, and John Locke. They compared their terms to Greek and treated logos, ratio, raison, and reason as interchangeable.

  Thomas Hobbes also used the word ratiocination as a synonym for reasoning. The source notes a subtle split in usage that survives today. As an abstract noun, reason names a faculty, while a reason is a single consideration that explains or justifies an event, a phenomenon, or someone's conduct. The adjective philosophers reach for is rational, rather than reasoned or reasonable.

• 3. A Cosmos That Reasons

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  Perhaps starting with Pythagoras or Heraclitus, the cosmos itself was said to have reason. For many classical philosophers, nature was understood teleologically, meaning every type of thing had a definitive purpose fitting within a natural order that had aims of its own. Reason, on this account, was not merely something people happened to possess; it linked an apparently immortal part of the human mind with the divine order of the cosmos.

  Plato described reason within the soul as a natural monarch, the part that should rule over spiritedness, called thumos, and the passions. His student Aristotle defined the highest human happiness, eudaimonia, as a life lived consistently and excellently in accordance with reason. The conclusions to be drawn from their discussions are among the most debated in the history of philosophy.

  In the neoplatonist account of Plotinus, the cosmos has one soul that is the seat of all reason, and the souls of all people are parts of it. Reason both gives form to material things and acts as the light that brings souls back into line with their source. This teleological inheritance would soon pass into the hands of theologians.

• 4. Faith Meets The Schoolmen

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  The greatest of the early Church Fathers, including Augustine of Hippo, Basil of Caesarea, and Gregory of Nyssa, were as much Neoplatonic philosophers as Christian theologians. They adopted the Neoplatonic view of human reason and its implications for the relationship between people, creation, and God. The same conception of the soul's rational aspect spread to medieval Islamic philosophers and still holds significance in Iranian philosophy.

  As European intellectual life reemerged, the influence of Averroes and Avicenna helped shape the Scholastic view of reason. Among the Scholastics, none was more influential than Saint Thomas Aquinas, who placed reason at the heart of his Natural Law. Because reason is a spark of the divine, Thomas concluded that every human life is invaluable, all humans are equal, and each is born with permanent basic rights. On this foundation, the idea of human rights was later built by Spanish theologians at the School of Salamanca.

  Other Scholastics took reason in a different direction. Roger Bacon and Albertus Magnus, following the Islamic scholar Alhazen, emphasized reason as a human ability to decode the created order and the structures underlying physical reality. This reading of reason was instrumental to the development of the scientific method in the early universities of the high Middle Ages.

• 5. The Thinking Thing

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  In the 17th century, Rene Descartes explicitly rejected the traditional notion of humans as rational animals. He suggested instead that they are nothing more than thinking things, of a piece with other things in nature. Searching for a foundation of all possible knowledge, he doubted everything except the mind in the act of thinking, writing, "I am therefore precisely nothing but a thinking thing; that is a mind, or intellect, or understanding, or reason."

  This became known as subject-centred reason, grounded in the knowing subject who studies and masters the rest of the world as objects. Descartes broke with tradition by refusing to divide the incorporeal soul into parts like reason and intellect, describing it instead as one indivisible entity. His contemporary Thomas Hobbes called reason a broader form of addition and subtraction not limited to numbers, an understanding sometimes termed calculative reason.

  David Hume pushed the line of thought toward skepticism, proposing that cause and effect cannot be deduced, so no knowledge rests on reasoning alone. He declared that reason "is, and ought only to be the slave of the passions." Hume even argued that animals have reason, only much less complex than the human kind.

• 6. Universal Law

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  In the 18th century, Immanuel Kant set out to show Hume was wrong by demonstrating that a transcendental self was a necessary condition of all experience. On the basis of such a self, he argued, reason could examine both the conditions and the limits of human knowledge. The great achievement of reason, in his German term Vernunft, is its capacity to exercise a kind of universal law-making across moral, theoretical, and aesthetic domains.

  Kant's categorical imperative captured this in a single rule: "Act only according to that maxim whereby you can, at the same time, will that it should become a universal law." Under practical reason, a person's moral freedom depends on the ability to behave according to laws reason gives them, rather than laws drawn from religion or nature. He held that pure reason could solve metaphysical problems through what he called transcendental logic, a theoretical science in its own right.

  Jurgen Habermas later argued that this substantive unity of reason has dissolved, so it can no longer answer the question, "How should I live?" He split reason into three autonomous spheres modeled on Kant's three critiques: cognitive-instrumental reason used by the sciences, moral-practical reason used to deliberate in the moral and political realm, and aesthetic reason found in works of art and literature. For Habermas these are the domain of experts and need mediating with the lifeworld by philosophers.

• 7. Symbols And Recollection

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  A dog once kicked can learn to recognize the warning signs and avoid being kicked again, yet the source insists this does not mean the dog has reason in any strict sense. Hobbes, Locke, and Hume all granted that some animals manage associative thinking, even linking causes and effects. For reason to be involved, an association like smoke and fire must be thought through and explained, which Locke said requires the mental use of a third idea in a syllogism.

  Charles Sanders Peirce held that reason in the strict sense requires creating and manipulating a system of symbols, where a symbol has only a nominal, habitual connection to the thing it stands for. Language is one such system. Hobbes described the creation of "Markes, or Notes of remembrance" as speech, using the word speech as an English version of logos, and called the marks Signes once they were communicated.

  Merlin Donald connects reason to mimesis, which he distinguishes sharply from mere imitation because it involves inventing intentional representations. He notes that a dog might perceive the meaning of a play-acted fight but could not distinguish the representation from a real fight, while trained apes and young children make the distinction easily. Plato called the related faculty eikasia, the ability to perceive that a dream, a memory, or a reflection in a mirror is not reality itself. Donald also emphasizes the ancient Greek anamnesis, recollection, the deliberate search to recapture something once known; as Jacob Klein put it, "To become aware of our having forgotten something means to begin recollecting."

• 8. The Quarrels Of Reason

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  Hamann, Herder, Kant, Hegel, Kierkegaard, Nietzsche, Heidegger, Foucault, and Rorty all contributed to a long debate over what reason ought to mean. Some, like Kierkegaard, Nietzsche, and Rorty, grew skeptical of subject-centred or instrumental reason, even of reason as a whole. Michel Foucault, in his essay "What is Enlightenment?", drew on Kant's split between private reason, used when one is a cog in a machine, and public reason, used when one reasons as a member of reasonable humanity, where its use must be free and public.

  The quarrel between reason and faith has been figuratively summarized as Athens and Jerusalem. Stephen Jay Gould argued there need be no conflict because reason and religion are each authoritative in their own magisterium. Joseph Ratzinger, later Benedict XVI, asserted that "Christianity has understood itself as the religion of the Logos," pointing to the line usually translated "In the beginning was the Word." Leo Strauss, influenced by the Muslim philosopher Al-Farabi, spoke of a Greater West held together by the tension between Greek rationalism and Abrahamic revelation.

  The sharpest challenge came from Rousseau, who proposed in his second Discourse that reason and political life are not natural and may even be harmful. He saw two principles prior to reason in human nature: an intense interest in our own well-being, and an objection to the suffering of any sentient being like ourselves. Rousseau argued that reason, language, and rational community developed slowly because some habits of cooperation solved certain problems, a view that later found support in Charles Darwin's Theory of Evolution. His initial impact encouraged bloody revolutions, including the French Revolution and the Russian Revolution, yet his own conclusions about the best community were remarkably classical, favoring city-states such as Geneva and rural living.