Yes human beings are a part of nature, just as all living organisms are. The question is important, however, since Western philosophy-from Christianity to the founders of Modern science itself-has tended to assume that we are somehow "outside" of, or "superior" to nature. The implication is that we can do what we like to the natural world both without moral concern, and without affecting ourselves. As the old saying goes, "the philosophy of one century is the common sense of the next." And that is our current problem.
The origin of the confusion is traceable to the philosophy of Rene Descartes, one of the founders of modern science. It was Descartes who penned one of the most famous lines in the history of Western philosophy-"I think, therefore I am." Or in the original Latin (the language of scholarship at the time), /cogito ergo sum/.
Descartes was a rationalist who felt that he needed a certain proposition from which to deduce the rest of his philosophy (think of Sherlock Holmes' methods in fiction). He proposed that "I think, therefore I am" was such a statement, and built his arguments from there. He further argued that from this statement he could deduce that the world was made up of two different types of substances-"thinking substance" and "extended substance." Thinking substance referred to the mind, while extended substance referred to the body. The resulting "separation" of mind and body is known as Cartesian dualism in the philosophical literature. This fundamental dualism is also consistent with the common dichotomies between subject/object, values/facts and humans/nature in modern Western philosophy. It has also been institutionalized in our institutions of higher learning through their separation into the faculties of Arts and Science.
The problem is that Descartes, even though he was one of the founders of scientific philosophy, was influenced by Christian thinking. His writings even contained a rational "proof" of God's existence. Not surprisingly, his conception of mind equated it with the concept of the human soul. The mind was considered to have no place in nature, and to be the true subject of our life. It was also pictured as a sort of "place" that could be looked into. Nature itself was pictured as a purely mechanical realm of meaningless forces and impacts, while all meaning and values were confined to humans-to the sphere of mind.
One of the implications of such a view is that our actions upon nature can never have any influence upon ourselves. This is because our essential selves-our minds-are pictured as "outside" of natural processes. As Gilbert Ryle (1949) so famously suggested, the human mind was viewed as "a ghost in the machine," which transcended the deterministic realm of nature.
The idea that humans are not a part of nature, however, is absurd from the perspective of contemporary ecological science. In fact, the relationship between an individual organism and the larger ecological context of which it is a part, is an /enabling condition/ for the life of any organism, including humans.
One need look no further than one's own daily life in order to confirm this. For with each breath of air which we take, with each glass of water which we drink, and with each bite of food which we eat, the dependence of our individual lives upon their ecological context is amply demonstrated. Each of these relationships involve necessary material exchanges with the world around us.
Indeed, each of these relationships demonstrates that our lives are intimately intertwined with the natural cycles in which we participate. The oxygen which we and other animals breathe is provided by plants, for example, which produce the oxygen from the carbon dioxide which we and other animals have exhaled. The animal and the vegetable are thus complementary poles of a causal cycle, each of which produce what the other requires.
Similarly, each time that we drink we participate within the larger hydrological cycle, within which all of the waters of the Earth are interconnected in a natural cycle of evaporation, transpiration, cloud formation, precipitation, run-off and evaporation. Since the waters of the Earth quite literally flow through us daily, this interrelationship must also be considered to be an essential aspect of our lives, as it is of all life on Earth.
Through eating we are also intimately connected to other forms of organic life. We literally consume their substance so that we might continue to live ourselves, which provides the energy our bodies require to go on living. In fact, we are dependent not only upon those species which we directly consume, but also upon all of the natural conditions which they, in turn, require for their existence.
Finally, so as not to ignore the "dirty" half of these relationships with our ecological context; we also urinate, defecate, spit, sweat, bleed, blow our noses, clip our fingernails, lose our hair, shed our skin in tiny fragments, and in various other ways return our bodily substance to the Earth on a daily basis, even long prior to our death. And of course when do eventually die, we return our bodies to the earth, which provide the material from which other lives may grow.
Thus life, when viewed as an empirically observable /process/, does not end at our skin. It is not a subjective, metaphysical property somehow hiding inside us as Descartes suggested. Rather, from a scientific perspective, life consists in these objective patterns of relationship with both our organic and inorganic environments. These relationships are essential aspects of our life itself. Quite simply, this is why we die if deprived of food, water or air for sufficient periods of time-for in these relationships do our lives consist.
As ecology is slowly teaching us, if we pollute the world around us, we also pollute ourselves. This is because our lives are intrinsically and intimately linked to these natural processes, which we could not exist without. And no amount of philosophy can ever change that.
So as Rachel Carson once put it, from an ecological and scientific perspective "Man, however much he may like to pretend the contrary, is a part of nature" (1962:188).
References, additional readings:
Rachel Carson (1962) Silent Spring, Houghton Mifflin Company.
Rene Descartes (1980) Discourse on the Method of Rightly Conducting Ones Reason and For Seeking Truth in the Sciences, translated by Donald A. Cress, Hackett Publishing Co.
Rene Descartes (1988) Selected Philosophical Works, translated by John Cottingham, Robert Stoothoff and Dugald Murdoch, Cambridge University Press.
Carolyn Merchant, (1990) The Death of Nature: Women, Ecology and the Scientific Revolution, HarperCollins.
Gilbert Ryle (1949) The Concept of Nature, Penguin.