Reason

Reason is the human capacity to consciously apply logic to find the truth. It involves drawing valid conclusions from both new and existing information. By using the intellect, people can extrapolate from known facts to generate new knowledge. This process is a way for thinking to move from one idea to a related one. It helps us understand the significance of sensory information from our environment. It also allows us to grasp abstract concepts like cause and effect, or truth and falsehood.

There are several specific ways that logical reasoning can be organized. One method is deductive reasoning, where conclusions follow necessarily from premises. Another is inductive reasoning, which involves making generalizations from specific observations. A third type is abductive reasoning, which seeks the most likely explanation for a set of facts. Philosophers also distinguish between these formal processes and intuitive reasoning. Intuition is a way of knowing that may be valid but can feel personal or subjective. In mathematics, intuition is often a vital part of the creative process used to reach a formal proof.

The history of the word "reason" is tied to ancient languages. The English word comes from the Latin term "ratio." This Latin word was used to translate the Greek term "logos." In Greek, "logos" could mean speech, an explanation, or even an account of money. Early English philosophers like Francis Bacon and John Locke wrote in Latin and French. They often treated the Greek, Latin, and English terms for reason as interchangeable. Some thinkers, such as Thomas Hobbes, even used the term "ratiocination" as a synonym for the act of reasoning.

In classical Greece, many philosophers believed reason linked humans to the cosmos. They viewed the universe through a teleological lens, meaning everything had a specific purpose. Some thinkers, like Pythagoras or Heracetitus, suggested the cosmos itself possessed reason. Plato described reason as a "natural monarch" within the human soul. He believed reason should rule over the passions and spiritedness. Aristotle, a student of Plato, famously defined humans as "rational animals." He argued that the highest form of human happiness comes from living in accordance with reason.

These classical ideas deeply influenced religious philosophy for centuries. Neoplatonists like Plotinus believed the cosmos had one soul that served as the seat of all reason. Early Christian thinkers, such as Augustine of Hippo, adopted these Neoplatonic views. During the Middle Ages, Islamic scholars like Avicenna and Averroes also held these views in high regard. This knowledge helped shape the Scholastic view of reason in Europe. Saint Thomas Aquinas used reason to develop his doctrine of Natural Law. He argued that because reason is a spark of the divine, all humans possess equal and intrinsic rights.

The early modern era brought significant changes to how reason was understood. Scientists began to move away from the idea that nature has its own aims or purposes. In the 17th century, René Descartes rejected the idea of humans as "rational animals." He instead described humans as "thinking things" that exist within the laws of nature. Descartes used reason to try and find a foundation for all knowledge. He famously doubted everything except the existence of his own mind while thinking. This approach is known as "subject-centred" reason because it focuses on the individual who perceives the world.

Other philosophers during this period offered different perspectives on the power of reason. Thomas Hobbes described reason as a form of "calculative" reasoning, similar to addition and subtraction. Later, David Hume took a more skeptical approach to the subject. Hume argued that reason cannot prove the relationship between cause and effect. He famously suggested that reason should be the "slave of the passions" rather than their master. Today, the study of reason continues through many different fields. Psychologists study the neural processes of thinking, while computer scientists study automated reasoning to model logic in machines.