You have to imagine the times in which Rousse lived. He was born (I think) around 1712. He grew up in a Europe where there was a corruption of power (as there is most of the time during the history of humanity). The Church still had its strong grip on people by controlling the destiny of their souls (or so they thought). The government and wealthy societies, which became known as the aristocrats, dominated the physical side of the people. The vast majority of people were dirt poor and totally submissive to those two entities.
It is interesting that the aristocrats justified their minority dominating the majority through reason. It was Aristotle, the father of modern reason, that promoted the concept of the philosopher-king. But what he meant was the most educated and rational people should lead society. But the French aristocrats (so named for the philosopher), while being the most educated, did not merge that with morality. There was very little compassion as exemplified in Marie Antoinette's famous line (when speaking about the starving masses) when she was told her subjects had no bread (meaning no food, period), "let them eat cake."
It was this moral corruption that drove Rousse to try and figure out the more perfect society. He was building on the philosophical backs of many others, such as the rationalist Descartes (who died about 20 years before Rousse was born) as well as the English rationalist, Hume et al.
But Rousse came to the philosophical conclusion that humans were most moral, and civil, while they were still animals. This was in stark contrast to the Church, which had been quite dualistic, seeing nature as not only fallen, but evil. Therefore, man (speaking of humanity) was evil in is most primitive state.
Rousse believed that when man rose from the dirt, where humans dwelled with the animals, that man became arrogant seeing himself above nature. When this arrogance took hold man also began to be controlled by comparisons (with each other, thus the social classes and wars between nations). He thought that if civil authority was removed and humanity would be allowed to return to it primal roots, that order and morality would return (what was later labeled, by others, the "noble savage" state).
Rousse's thinking was part of the ground swell that fueled the eventual French Revololution. They had the notion that if they threw out the authority figures, that bliss would come. But of course it didn't as exemplified by the Reign of Terror or say if you've read the book or seen the movie Les Miserables . . . or if you have read the book Animal Farm, you will get the jest. It was a horrible exercise in returning the free, wild and natural.
But the thought of "natural" began to take root in writing, art and in culture in general. It took almost 200 years for the thought to reach its zenith in American culture.
But "natural" isn't a scientific term or any type of natural (pardon the pun) division within reality. It is an artificial division reflecting the simple notion proposed by Rousse, that if man (meaning mankind) touched it, then it is inferior. In its non-human touched form, it is superior.
But Madison Ave. (meaning of course the advertising world) has cashed in on this notion of "natural" being super, good, clean and "chemical" meaning harmful, inferior or even immoral.
But the bigger issue is the fact that throughout history the Church has embraced secular philosophies and incorporated them within their theology. But this is true of all human endeavors and not just the Church. As you are doing this incorporation, you are totally naïve to the process.
So I find it interesting that many of my Christian friends advocate organic farming, natural health care and the list could go on, as Christian virtues.
My point here, once again, is that all is created, man, the things that people refer to when they say nature, the universe, the spiritual, the psychological, the intellectual . . . all fall into the same category. They were all created good. Then the fall tainted things so nothing works quite right, but none of it became evil. So when you contrast one part of creation . . . than part touched by man against the other side, the untouched or what Madison Ave. means by "natural" one is not better than the other. If the fall is real, then the course of Christian history should be to restore all, including nature.