D.Phil. (Nematology) / The science of taxonomy or the organisation and labelling of organisms may strike many as dull and stuffy but everyone working in this fascinating field finds that it leads to some of the most searching and interesting questions. Taxonomists are confronted by a well organised world of nature, exactly that what prompted the great taxonomist Linnaeus to develop his clear, hierarchical method of classification. But at the same time they are faced with a bewildering diversity and variation within this organised whole. Seeking to order the stable units in the midst of this diversity is the descriptive task of taxonomy. But many taxonomists go further than that, they seek a theory and ask: what causes life to be ordered? Here they land in the middle of philosophical debate and controversy. The field of taxonomy has, unfortunately, been divided by arguments about what a species is, how to demarcate a species, and even whether they are real or not. Today this "species question" is phrased in broader terms. The real question is not whether species are fixed but whether there is any stable, objective unit in nature. What do the patterns of similarity and difference mean - creation according to a common plan with the potential of variation, or descent from a common ancestor with modifications? Charles Darwin believed that change is unlimited, that species are infinitely variable. He thought that species could vary indefinitely and in any direction. Creationists on the other hand, believe that change is limited by a basic organic "unit", the "created kind" and within the boundary of that fundamental unit, variation can be profuse, but it can never lead to the creation of a new basic type. This is near the essentialism as taught by Aristotle nearly 2000 years ago. Aristotle thought that each species embodies an eternal, unchanging ideal or archetype. The problem with this view is that it assumed a single form or pattern. Most biologists until the time of Darwin held to the typological view, a view considered by many scientists today as very plausible. This theory holds that the organic world is discontinuous, that all major groups of organisms are separate and breed true to type. A species is also defined by a cluster of characteristics - each member of the species may have some but not all of the diagnostic features. Another view is cladism, founded by the entomologist, Willy Hennig. It is concerned with the patterns found in nature and involves the finding of the positive and verifiable characters of the various species and determining how all species fit into the animal kingdom.