Reason

• 1. Defining Rational Capacity

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  Reason is the capacity of consciously applying logic by drawing valid conclusions from new or existing information, with the aim of seeking truth. This ability distinguishes humans from other species and underpins activities like philosophy, religion, science, language, and mathematics. Aristotle drew a distinction between logical discursive reasoning and intuitive reasoning, noting that intuition may tend toward the personal and subjectively opaque. In some social settings, these modes clash, while in others they complement each other. Mathematics often requires intuition to arrive at formal proofs, which are among the most difficult tasks of formal reasoning. Reasoning allows rational individuals to understand sensory information and conceptualize abstract dichotomies such as cause and effect, truth and falsehood, or good and evil. It serves as part of executive decision making, enabling people to self-consciously change goals, beliefs, attitudes, traditions, and institutions. This capacity for freedom and self-determination remains central to how we define human nature.

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• 2. Classical Philosophical Foundations

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  For many classical philosophers, nature was understood teleologically, meaning every type of thing had a definitive purpose within a natural order. Perhaps starting with Pythagoras or Heraclitus, the cosmos itself was said to have reason. Plato described reason as the natural monarch ruling over spiritedness and passions within the human soul. His student Aristotle defined human beings as rational animals, emphasizing reason as a core characteristic of human nature. He described the highest human happiness as a life lived consistently, excellently, and completely in accordance with reason. Neoplatonist Plotinus argued the cosmos has one soul serving as the seat of all reason, with individual souls being parts of this universal soul. Early Church Fathers like Augustine of Hippo, Basil of Caesarea, and Gregory of Nyssa adopted these Neoplatonic views alongside Christian theology. Medieval Islamic scholars including Averroes and Avicenna further developed these ideas before European intellectual life reemerged from the Dark Ages. Saint Thomas Aquinas placed reason at the heart of Natural Law, concluding that because humans possess reason as a spark of the divine, every single human life is invaluable. This foundation later enabled Spanish theologians at the School of Salamanca to construct modern concepts of human rights.

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• 3. Modern Epistemological Shifts

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  In the 17th century, René Descartes explicitly rejected the traditional notion of humans as rational animals, suggesting instead they are nothing more than thinking things. He brought into doubt all knowledge except that of the mind itself in the process of thinking. This became known as epistemological or subject-centred reason, based on the knowing subject who perceives the world as objects to be studied. A contemporary of Descartes, Thomas Hobbes described reason as a broader version of addition and subtraction not limited to numbers. In the late 17th century through the 18th century, John Locke and David Hume developed Descartes's line of thought further. Hume took it in an especially skeptical direction, proposing there could be no possibility of deducing relationships of cause and effect. He famously remarked that reason is and ought only to be the slave of the passions. Immanuel Kant attempted to show that Hume was wrong by demonstrating that a transcendental self was a necessary condition of all experience. Kant claimed reason could be used to find solutions to metaphysical problems, especially the discovery of the foundations of morality. Jürgen Habermas later argued that the substantive unity of reason has dissolved in modern times, leaving only formal procedures.

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• 4. Critiques and Contemporary Debates

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  Thinkers like Kierkegaard, Nietzsche, and Rorty have been skeptical about subject-centred, universal, or instrumental reason, questioning its validity altogether. Hegel believed reason had obscured the importance of intersubjectivity or spirit in human life, attempting to reconstruct what reason should be. Michel Foucault proposed a critique based on Kant's distinction between private and public uses of reason. Private reason applies when an individual acts as a cog in a machine with specific social roles, while public reason functions when one reasons as a member of reasonable humanity. Charles Taylor proposed that reason ought to include the faculty of disclosure tied to how we make sense of things in everyday life. Nikolas Kompridis offered a view of reason as that ensemble of practices contributing to opening and preserving openness in human affairs. These debates question whether there is just one rationality or multiple systems that may conflict without any super-rational system to resolve them. The tension between unaided reason and faith in revealed truths remains a defining feature of Western civilization, summarized figuratively as Athens and Jerusalem.

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• 5. Scientific Inquiry into Cognition

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  Psychologists attempt to determine whether people are capable of rational thought in various circumstances through behavioral experiments. Research focuses on how people perform on tests like intelligence or IQ assessments and how well their reasoning matches ideals set by logic. Examiners study how individuals make inferences from conditionals like if A then B and alternatives like A or else B. Developmental psychologists investigate reasoning development from birth to adulthood, with Piaget's theory being the first complete framework for cognitive development. Neurophysiologists and cognitive neuroscientists study the biological functioning of normally functioning brains alongside damaged or unusual ones. Clinical psychologists work to alter unhelpful reasoning habits when those patterns hinder mental health. In computer science, scientists use automated reasoning for diverse applications including automated theorem proving and formal semantics of programming languages. Meta-reasoning allows systems to observe and modify their own structure and behavior through reflection capabilities built into specific programming languages.

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• 6. Evolutionary and Social Origins

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  French social and cognitive scientists Dan Sperber and Hugo Mercier argue that other forces beyond individual benefit drove the evolution of reason. They point out that reasoning is very difficult for humans to do effectively, especially when doubting one's own beliefs due to confirmation bias. Reasoning proves most effective when done as a collective, demonstrated by the success of projects like science. Any group managing to find ways of reasoning effectively would reap benefits for all members, increasing evolutionary fitness. This suggests pressures exist not just individually but through group selection at play. Sperber's argumentative theory claims reason may have more to do with winning arguments than searching for truth. Rousseau in his Second Discourse claimed reason, language, and rationally organized communities developed over time merely because cooperation solved certain problems. Once such cooperation became important, it forced people to develop increasingly complex cooperation often only to defend themselves from each other. Charles Darwin's Theory of Evolution later provided support for this view that human nature is malleable rather than fixed.

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