The "Great Chain of Being"

Most of the concepts about the nature of living things derive from the writings of Aristotle (a Greek philosopher of the Fourth Century, B.C.).

From Aristotle we derive the concept of distinct types of organisms which could each be distinguished from all the rest. Aristotle was interested in much more than the biological world, and attempted to build a theory of the world as a whole. As part of this theory, he believed that all of nature could be seen as a continuum of organization from lifeless matter (e.g., water, Earth, fire and air) to the most complex forms of life.

He thought of humans as different from the rest of animals because of their capacity for reason or thought.

In fact reason is the capacity which differentiates man from animals, but Aristotle proposed a rank ordering of all living things, from the least to the highest (humans).

This idea developed, during the later centuries, into the concept of the "Great Chain of Being". The idea had become rigidly codified by the 14th century (preceeding the Renaissance). All living things were seen as members of unchanging types, called species, which could be ordered from the least to the highest.

The metaphor of the "chain" of being suggested that these species were linked to each other by a logical progression. This concept, in the Western tradition, is the result of the attempt to combine the Aristotelian philosophy and Christian theology.

This concept of reality was modified by the Renaissance, which broke with the medieval tradition of reliance on authority (for example, on Aristotle), and emphasized the importance of reliance on direct observation (science) or pure reason (philosophy).