Natural Philosophy

Quick Facts

• Name: Natural philosophy, or philosophy of nature
• Period: ancient Greek philosophy through the early modern period; the name stayed common into the 1800s
• Main region: Mediterranean and European learned traditions, with major Arabic, Jewish, and Latin medieval transmission
• Main subjects: nature, motion, matter, life, the heavens, causes, experiment, and laws
• Later descendants: physics, astronomy, chemistry, biology, and Philosophy of Science
• Basic shift: from explaining nature by forms, purposes, and causes to explaining it by experiment, mathematics, matter, motion, and forces

The Big Question

What kind of explanation makes nature intelligible?

For much of the tradition, the answer was: explain what a thing is, what it is made of, how it changes, and what end or function its changes serve. In the early modern period, many thinkers changed the answer: explain natural events by observation, controlled experiment, mathematical relations, matter in motion, and general laws.

In One Minute

Natural philosophy was the old broad name for the study of nature before the modern sciences split into separate fields. A natural philosopher could ask about falling stones, animal bodies, planets, light, elements, weather, magnets, and the structure of matter without treating these as separate professional sciences.

The tradition begins before Aristotle, but Aristotle gave it its most durable ancient framework. He treated nature as an ordered field of things that move and develop according to their own principles. Medieval thinkers taught, debated, and revised that framework in universities. Early modern thinkers such as Francis Bacon, Galileo Galilei, Rene Descartes, Robert Boyle, and Isaac Newton transformed the field by giving more authority to experiment, instruments, mathematical models, mechanism, and laws of nature.

Natural philosophy matters because modern science grew out of it. It also shows that "science" was never just a pile of facts. It depended on arguments about what counts as a good explanation.

Main Ideas

• Nature means the world of things that grow, move, decay, act, and interact without being human artifacts. A tree, a stone, a storm, and a planet count as natural. A chair counts as artificial, even though it is made from natural materials.
• A cause is an explanation of why something is the way it is. Aristotle's famous four causes are material cause, or what something is made of; formal cause, or its structure; efficient cause, or what brings it about; and final cause, or the end it serves.
• Motion meant more than movement from place to place. In Aristotelian language it meant change: a seed becoming a plant, cold water becoming hot, a body growing, or a stone falling.
• Matter is the stuff out of which physical things are made. Older theories used elements such as earth, water, air, and fire. Early modern theories increasingly used particles, corpuscles, or bodies with size, shape, and motion.
• Teleology means explanation by ends or purposes. Saying "roots are for drawing water" is teleological. Early modern physics largely rejected teleology for motion and mechanics, though biology still uses function language in a more careful way.
• Experiment means actively testing nature under arranged conditions. Dropping balls on an inclined plane, using an air pump, or passing light through a prism are experiments because the investigator sets up a situation to force a clearer answer.
• Mathematization means treating natural processes as measurable relations. Instead of saying "heavy bodies seek the center," Galileo asks how far a body falls in a given time.
• Mechanism explains natural events by parts, shape, size, impact, pressure, and motion. A mechanical philosopher tries to explain heat, light, breathing, or magnetism without hidden forms or built-in purposes.
• Laws of nature are general rules that describe how bodies behave. Newton's laws of motion and law of universal gravitation made this model of explanation dominant in physics.

How It Works

Ancient natural philosophy asked what the world is made of and why it changes. The Presocratics proposed bold answers: water, air, number, atoms, flux, or unchanging being. Aristotle gave the most systematic version. His natural philosophy studied bodies that have an internal source of change. Living things grow from within. Heavy bodies fall. Fire rises. Animals perceive and move.

Aristotle's method mixed observation, classification, conceptual analysis, and argument. He studied animals closely, but he also wanted explanations that fit into a larger picture of nature. A good answer did not just say what happened. It said what kind of thing was involved, what its powers were, what caused the change, and what completed state the change tended toward.

Medieval natural philosophy was built around Aristotle's natural works, especially in university teaching. Scholastic thinkers commented on texts, raised objections, and debated hard cases. Projectile motion was one famous problem: if motion requires a mover, why does an arrow keep moving after it leaves the bow? Medieval discussions of impetus, acceleration, optics, and the heavens helped prepare later changes, even when the official curriculum still sounded Aristotelian.

Renaissance and early modern natural philosophy did not change all at once. Many thinkers still used Aristotle, but they also faced new astronomy, anatomy, navigation, instruments, printing, and recovered ancient atomism. The field became a contest over method. Should natural philosophy begin from inherited principles, from mathematical models, from experiments, from metaphysical first principles, or from collections of observed facts?

Bacon argued that the mind jumps too quickly to grand theories. He wanted natural philosophers to gather careful "histories" of phenomena, design experiments, correct mental errors, and move slowly from particulars to broader claims. Boyle turned this experimental program into a public practice: report procedures, record failures, invite witnesses, and build cautious explanations from many trials.

Galileo pushed another change: mathematics belongs inside natural philosophy. He used geometry, measurement, and idealized cases to study falling bodies and projectiles. Descartes offered a different but related program: explain the physical world through matter as extension and motion according to laws. Newton then joined mathematics, experiment, and force into a new model. In the Principia, the same gravitational force explains falling bodies, the Moon, planets, tides, and comets.

Key Ideas With Examples

• Four causes: A bronze statue has a material cause, the bronze; a formal cause, the statue's shape; an efficient cause, the sculptor's work; and a final cause, perhaps honoring a person. Aristotle thought natural things also needed this range of explanation. An acorn is not just wood-stuff being pushed around. It develops toward the form of an oak.
• Natural motion: In Aristotle's physics, earthly bodies tend toward their natural places. A stone falls because its element-like nature tends downward. Early modern physics rejected this as an explanation. It asked instead for rules connecting distance, time, acceleration, mass, and force.
• Final causes: A heart can be explained by what it does for the body. That kind of explanation felt natural in biology. But for falling rocks or planetary motion, early modern thinkers increasingly wanted efficient causes: what pushes, pulls, attracts, collides, or mathematically governs the motion.
• Experiment and instruments: A telescope made the moons of Jupiter visible. An air pump let Boyle study pressure, vacuum, and respiration under artificial conditions. These tools did not just add facts. They changed what counted as evidence.
• Mechanism: A mechanist tries to explain nature as if it were made of interacting parts. For Descartes, bodies are extended things moving in a plenum, a filled space with no true vacuum. For Boyle, corpuscles with size, shape, arrangement, and motion explain many qualities of matter.
• Mathematization: Galileo's study of falling bodies replaces a qualitative contrast between "light" and "heavy" with measurable relations. Newton's inverse-square gravity says the attractive force between bodies changes with mass and distance. This made prediction and correction central to natural knowledge.
• Action at a distance: Newton's gravity worked mathematically, but critics asked how one body could attract another through empty space. Newton did not give a mechanical contact story for gravity. That was part of the debate: can a law be accepted before we know the hidden mechanism?

Key People

• Aristotle: built the classic framework of nature, causes, motion, form, matter, and purpose.
• Democritus and Lucretius: defended atomist alternatives that explained nature through atoms, void, and motion.
• John Philoponus: criticized parts of Aristotle's physics and influenced later debates about motion.
• Robert Grosseteste, Roger Bacon, and Nicole Oresme: show the medieval use of mathematics, optics, experiment, and arguments about motion inside a broadly Aristotelian world.
• Thomas Aquinas: integrated Aristotelian natural philosophy with Christian theology.
• Francis Bacon: argued for a reform of knowledge through experiment, induction, and the correction of mental habits.
• Galileo Galilei: made mathematics central to the study of motion and defended the physical possibility of a moving Earth.
• Rene Descartes: tried to rebuild natural philosophy from metaphysics, matter as extension, and mechanical laws of motion.
• Robert Boyle: developed experimental philosophy, corpuscular explanations of matter, and public reporting of experiments.
• Isaac Newton: turned natural philosophy toward mathematical laws of motion and universal gravitation.
• Margaret Cavendish: criticized overconfidence in instruments and rejected the idea that matter is merely dead and passive.

Important Works

• Aristotle, Physics: sets out nature, change, place, time, motion, and causes. It is the foundation text for ancient and medieval natural philosophy.
• Aristotle, On the Heavens and On Generation and Corruption: develop his cosmology, element theory, and account of coming-to-be and passing-away.
• The Advancement of Learning, by Bacon: defends the reform and organization of knowledge for public benefit.
• Novum Organum, by Bacon: attacks mental "idols," or recurring sources of error, and proposes disciplined induction and experiment as a new instrument for discovering nature.
• Galileo, The Assayer: argues that the "book of nature" is written mathematically and attacks purely bookish natural philosophy.
• Galileo, Two New Sciences: studies strength, falling bodies, acceleration, and projectile motion, showing how mathematics can recast old questions about motion.
• Discourse on Method and Principles of Philosophy, by Descartes: connect method, metaphysics, matter, motion, and a mechanical picture of nature.
• Robert Boyle, The Sceptical Chymist: challenges older element theories and helps move chemistry away from Aristotelian and alchemical frameworks.
• Robert Boyle, Some Considerations Touching the Usefulness of Experimental Natural Philosophy: defends experimental inquiry as useful, cumulative, and religiously serious.
• Newton, Philosophiae Naturalis Principia Mathematica: gives laws of motion and universal gravitation, unifying terrestrial and celestial motion under one mathematical framework.
• Newton, Opticks: reports experiments on light and color and ends with "Queries" that shaped later thinking about matter, forces, and method.
• Observations upon Experimental Philosophy, by Cavendish: criticizes experimental culture, microscopes, and mechanism while defending active matter.

Why It Matters

Natural philosophy is the bridge between ancient philosophy and modern science. It explains why Aristotle appears in the history of physics, why Newton's greatest work still has "natural philosophy" in the title, and why early modern science was also a philosophical battle over method.

It also keeps the history from becoming too simple. The Scientific Revolution was not just "people finally looked at facts." Aristotle observed nature. Medieval thinkers argued carefully about motion. Early modern thinkers disagreed with each other about experiment, mathematics, mechanism, vacuum, atoms, gravity, and God. What changed was the standard for explanation.

Modern science inherits many early modern habits: measurement, public evidence, repeatable experiments, mathematical laws, and suspicion of explanations that merely rename the problem. Modern philosophy of science inherits the questions left behind: What is a law? How do experiments support theories? When is an unobservable entity acceptable? How much should science rely on models, instruments, and idealizations?

Proponents, Critics, and Opponents

Aristotelians defended a nature filled with forms, powers, and purposes. Scholasticism preserved and debated that framework in medieval universities. It was not one frozen doctrine, but it gave European natural philosophy its standard vocabulary.

Bacon, Boyle, and the experimental philosophers criticized reliance on inherited systems and verbal explanation. They wanted nature tested, handled, recorded, and made useful. Galileo and Newton criticized older qualitative accounts of motion by replacing them with mathematics. Descartes criticized scholastic forms and qualities, but he was more rationalist than Bacon: he wanted physics grounded in clear principles about matter and motion.

The critics of the new natural philosophy were not all anti-science. Cavendish thought experimentalists overtrusted instruments and made matter too passive. Some Cartesians and Leibnizians objected that Newtonian gravity looked like an unexplained action at a distance. Aristotelians complained that mechanism could describe motions but not fully explain life, purpose, and form. Those disputes helped define what modern science would count as a good answer.

Related Pages

• Aristotle
• Aristotelianism
• Scholasticism
• Early Modern Philosophy
• Francis Bacon
• Novum Organum
• Galileo Galilei
• Rene Descartes
• Principles of Philosophy
• Isaac Newton
• Empiricism
• Rationalism
• Philosophy of Science
• Observations upon Experimental Philosophy