Natural philosophy or philosophy of nature was the philosophical study of nature and the physical universethat was dominant before the development of modern science. It is considered to be the precursor of natural science.

From the ancient world, starting with Aristotle, to the 19th century, the term "natural philosophy" was the common term used to describe the practice of studying nature. It was in the 19th century that the concept of "science" received its modern shape with new titles emerging such as

"biology" and "biologist", "physics" and "physicist" among other tech- nical fields and titles; institutions and communities were founded, and unprecedented applications to and interactions with other aspects of so- ciety and culture occurred. Isaac Newton's book Philosophiae Naturalis Principia Mathematica, whose title translates to "Mathematical Princi- ples of Natural Philosophy", reflects the then-current use of the words "natural philosophy", akin to "systematic study of nature". Even in the 19th century, a treatise by Lord Kelvin and Peter Guthrie Tait, which helped define much of modern physics, was titled Treatise on Natural Philosophy.

In the German tradition, Naturphilosophie persisted into the 18th and 19th century as an attempt to achieve a speculative unity of nature and spirit. Some of the greatest names in German philosophy are associated with this movement, including Goethe, Hegel and Schelling. Natur- philosophie was associated with Romanticism and a view that regarded the natural world as a kind of giant organism, as opposed to the philo- sophical approach of figures such as John Locke and Isaac Newton who espoused a more mechanical view of the world, regarding it as being like a machine.

The term natural philosophy preceded our current natural science. Empirical science historically developed out of philosophy or, more specifically, natural philosophy. Natural philosophy was distinguished from the other precursor of modern science, natural history, in that natu- ral philosophy involved reasoning and explanations about nature, whereas natural history was essentially qualitative and descriptive.

In the 14th and 15th centuries, natural philosophy was one of many branches of philosophy, but was not a specialized field of study. The first person appointed as a specialist in Natural Philosophy per se was Jacopo Zabarella, at the University of Paduain 1577.

Modern meanings of the terms science and scientists date only to the 19th century. Before that, science was a synonym for knowledge or study, in keeping with its Latin origin. The term gained its modern meaning when experimental science and the scientific method became a specialized branch of study apart from natural philosophy.From the mid- 19th century, when it became increasingly unusual for scientists to con- tribute to both physicsand chemistry, "natural philosophy" came to mean just physics, and the word is still used in that sense in degree titles at the University of Oxford. In general, chairs of Natural Philosophy established long ago at the oldest universities are nowadays occupied

mainly by physics professors. Isaac Newton's book Philosophiae Natu- ralis Principia Mathematica, whose title translates to "Mathematical Principles of Natural Philosophy", reflects the then-current use of the words "natural philosophy", akin to "systematic study of nature". Even in the 19th century, a treatise by Lord Kelvin and Peter Guthrie Tait, which helped define much of modern physics, was titled Treatise on Natural Philosophy.

In Plato's earliest known dialogue, Charmides distinguishes between science or bodies of knowledge that produce a physical result, and those that do not. Natural philosophy has been categorized as a theoretical rather than a practical branch of philosophy. Sciences that guide arts and draw on the philosophical knowledge of nature may produce practical results, but these subsidiary sciences go beyond natural philosophy.

The study of natural philosophy seeks to explore the cosmos by any means necessary to understand the universe. Some ideas presuppose that change is a reality. Although this may seem obvious, there have been some philosophers who have denied the concept of metamorphosis, such as Plato's predecessor Parmenides and later Greek philosopher Sextus Empiricus, and perhaps some Eastern philosophers. George Santayana, in his Scepticism and Animal Faith, attempted to show that the reality of change cannot be proven. If his reasoning is sound, it follows that to be a physicist, one must restrain one's skepticism enough to trust one's senses, or else rely on anti-realism.

René Descartes' metaphysical system of Cartesian Dualism describes two kinds of substance: matter and mind. According to this system, eve- rything that is "matter" is deterministic and natural – and so belongs to natural philosophy – and everything that is "mind" is volitional and non- natural, and falls outside the domain of philosophy of nature.

Major branches of natural philosophy include astronomy and cos- mology, the study of nature on the grand scale; etiology, the study of causes; the study of chance, probability and randomness; the study of elements; the study of the infinite and the unlimited; the study of matter; mechanics, the study of translation of motion and change; the study of nature or the various sources of actions; the study of natu- ral qualities; the study of physical quantities; the study of relations be- tween physical entities; and the philosophy of space and time.

Humankind's mental engagement with nature certainly predates civi- lization and the record of history. Philosophical, and specifically non- religious thought about the natural world, goes back to ancient Greece.

These lines of thought began before Socrates, who turned from his phil- osophical studies from speculations about nature to a consideration of man, viz., political philosophy. The thought of early philosophers such Parmenides, Heraclitus, and Democritus centered on the natural world. In addition, three presocratic philosophers who lived in the Ionian town of Miletus Thales, Anaximander, and Anaximenes, attempted to explain natural phenomena without recourse to creation myths involving the Greek gods. They were called the physikoi or, as Aristotle referred to them, the physiologoi. Plato followed Socrates in concentrating on man. It was Plato's student, Aristotle, who, in basing his thought on the natural world, returned empiricism to its primary place, while leaving room in the world for man. Martin Heidegger observes that Aristotle was the originator of conception of nature that prevailed in the Middle Ages into the modern era:

The Physics is a lecture in which he seeks to determine beings that arise on their own, τὰ υύσει ὄντα, with regard to their being. Aristoteli- an "physics" is different from what we mean today by this word, not only to the extent that it belongs to antiquity whereas the modern physi- cal sciences belong to modernity, rather above all it is different by virtue of the fact that Aristotle's "physics" is philosophy, whereas modern physics is a positive science that presupposes a philosophy. This book determines the warp and woof of the whole of Western thinking, even at that place where it, as modern thinking, appears to think at odds with ancient thinking. But opposition is invariably comprised of a decisive, and often even perilous, dependence. Without Aristotle's Physics there would have been no Galileo.

The scientific method has ancient precedents and Galileo exemplifies a mathematical understanding of nature which is the hallmark of modern natural scientists. Galileo proposed that objects falling regardless of their mass would fall at the same rate, as long as the medium they fall in is identical. The 19th-century distinction of a scientific enterprise apart from traditional natural philosophy has its roots in prior centuries. Pro- posals for a more "inquisitive" and practical approach to the study of nature are notable in Francis Bacon, whose ardent convictions did much to popularize his insightful Baconian method. The late 17th-century nat- ural philosopher Robert Boyle wrote a seminal work on the distinction between physics and metaphysicscalled, A Free Enquiry into the Vul- garly Received Notion of Nature, as well as The Skeptical Chymist, af- ter which the modern science of chemistry is named.

These works of natural philosophy are representative of a departure from the medieval scholasticism taught in European universities, and anticipate in many ways, the developments which would lead to science as practiced in the modern sense. As Bacon would say, "vexing nature" to reveal "her" secrets, rather than a mere reliance on largely historical, even anecdotal, observations of empirical phenomena, would come to be regarded as a defining characteristic of modern science, if not the very key to its success. Boyle's biographers, in their emphasis that he laid the foundations of modern chemistry, neglect how steadily he clung to the scholastic sciences in theory, practice and doctrine. However, he meticulously recorded observational detail on practical research, and subsequently advocated not only this practice, but its publication, both for successful and unsuccessful experiments, so as to validate individual claims by replication.