Richard E. Nisbett claims that “the greatest of Greek scientific discoveries was the discovery – or rather, as philosopher Geoffrey Lloyd put it, the invention – of nature itself, The Greeks defined nature as the universe minus human beings and their culture. Although this seems to us to be the most obvious sort of distinction, no other civilization came upon it. A plausible account of how the Greeks happened to invent nature is that they came to make a distinction between the external, objective world and the internal, subjective one” 
Pierre Hadot is a French philosopher known for his deep understanding of the ancient Greek thought. In his elegant masterpiece “The Veil of Isis”  he explains the evolution of the idea of nature from ancient Greek to modern times. The translator Michael Chase should be congratulated for the lucid English translation of the French original. The book is an intellectual tour de force. Pierre Hadot mentions that he was thinking about writing this book for 40 years. The outcome was a book of beauty and wisdom.
In this article I summarize the points he is making in “The Veil of Isis”.
Heraclitus said “What is born tends to disappear.” When this aphorism was cited in the Greek literature for the first time after five centuries it acquired a new meaning: “Nature loves to hide.” This is because the meaning of the word “phusis” evolved considerably. The word “phusis” had many meanings in Heraclitus’ time but it did not mean nature as a whole. In Heraclitus’ time “phusis” had two meanings: 1) proper constitution of each thing 2) genesis, appearance, growth. Five centuries later the concept of the “secret of nature” had developed. The aphorism reflected this new concept.
Empedocles & Parmenides
Empedocles spoke of the nature (phusis) of things. Parmenides spoke of the birth (phusis) of ether.
The word “phusis” in Hippocrates’ medical documents referred to the physical constitution of patients or what results from their birth, or what is congenital.
To Plato “phusis” meant the “essence” of things. Plato also used it in the phrase “phusis apeirou” to mean “the infinite”. He talked about “phusis” as the “divine art” within things. He believed, however, that this “divine art” or the “secrets of nature” were inaccessible to humans.
Aristotle defined nature (phusis) as a principle of inner motion inside each thing.
The stoics defined “phusis” as an artistic fire that engenders all things.
“The original fire gradually condenses into air, water, and earth, only to be set aflame once again after passing through the contrary phases. The world therefore has two aspects; the world taken in its formative and original aspect, and the world taken in the succession of its various states and its periodic becoming.” 
“Before the process has been set in motion, phusis, Nature, God, Providence, and divine Reason are identical, and God is alone. Once the cosmic process is deployed, Nature sinks into matter, to form and direct bodies and their interactions from within.” 
Nature as Secret
Stoics elaborated on this concept also. “The great secret of nature is thus Nature herself, that is, the invisible reason or force, of which the visible world is only the external manifestation. It is this invisible nature that ‘loves to hide’, or conceal itself from human view. Nature thus has a twofold aspect: it shows itself to our senses in the rich variety of the spectacle presented to us by the living world and the universe, and at the same time. it conceals itself behind appearances in its most essential, profound, and effective part.” 
After the emergence of the philosophical notion of nature in the first century BCE, Latin speaking philosophers no longer spoke of divine secrets but rather of the secrets of nature. The metaphor of “secrets of nature” appearing in the Hellenistic period dominated the Western thought for two millenia.
Middle Ages in Europe
A work known as “Secret of Secrets” translated from Arabic and wrongly attributed to Aristotle was very influential during middle ages in Europe. The popularity of Occult, Magic and Alchemy during middle ages shows clearly that the concept of “secrets of nature” was firmly established in European thought. When science emerged in the 17’th century it took over the task of unveiling the “secrets of nature”.
Attitudes Towards Nature
Attitude of Socrates
If Nature hides and conceals its secrets from us then we can adopt several attitudes. One attitude is to reject all research regarding Nature. This was the attitude taken by Socrates who focused on ethics and social philosophy.
Another attitude is the one adopted by modern physics which tries to unveil the secrets of nature by obliging Nature to answer its questions. Francis Bacon who is one of the founders of scientific method said “Let the human race recover his rights over nature, rights granted to it by divine munificence.”. Francis Bacon also used the metaphor of “interrogating nature”.
In the Promethean attitude one unveils the secrets of nature through technology. The physics experiments and technology can be considered as violence or tricks against nature. Hadot adds that in addition to experimentation and technology, magic also has the Promethean attitude because it aims to produce in nature movements that do not seem natural.
The Orphic attitude can be described as penetrating the secrets of nature not through violence but through melody, rhythm, and harmony. The Orphic attitude is unveiling the secrets of nature through discourse, poetry, and art. Hadot says “Wheras the Promethean attitude is inspired by audacity, boundless curiosity, the will to power, and the search for utility, the Orphic attitude, by contrast, is inspired by respect in the face of mystery and disinterestedness.”
Goethe was one of those who advocated the Orphic attitude. He contradicted Francis Bacon by saying that “Nature keeps silent under torture”. For Goethe, the only real way to discover the secrets of nature is through perception and the aesthetic description of perception.
Study of Nature as a Spiritual Exercise
Yet another attitude is the study of Nature as a spiritual exercise. This is the attitude I adopted. I was very pleased to discover that Hadot discusses this subject in his book “The Veil of Isis”. He points out the following aspects that should be considered as part of the study of Nature as a spiritual exercise:
- The Pleasure of Knowing
- The Study of Nature as an Ethics of Objectivity
- The Study of Nature in the Service of Mankind
 Richard E. Nisbett, “Geography of Thought”, Free Press (2003), ISBN 0-7432-5535-6
 Pierre Hadot, “The Veil of Isis”, Harvard University Press (2006), ISBN 978-0-674-02316-1