Polythetic classification

Clearly, a complete classification of separations would require an accounting based on similarities and differences in many properties. In taxonomy, this would be termed a polythetic classification, as opposed to monothetic classifications based on only one property. Monothetic classifications are not necessarily erroneous—they are simply incomplete. In a complex field such as separations, many monothetic classifications exist, each one different, each with an element of validity, but each incomplete. 

We found earlier that a theoretical consideration of displacement and transport exerts a unifying influence on separation science, bringing diverse methods under a common descriptive umbrella. The theory leads in a natural way to the formation of categories of separations which can be considered the beginning of a fundamental classificatory system. Here we generalize the results of transport theory to develop a fundamental basis for classification. While the resulting scheme will not be a complete polythetic classification, it will be based upon some of the most fundamental features of the separation process. These basic features, incorporated in the classification, should correlate well with other properties of separations in the same way that the number of outer-shell electrons is directly related to the diverse properties of the elements of the periodic table. This transport-oriented... 

Answeri The plant families did start their lives (in our history of knowledge) with monothstic sets, due to incomplete knowledge. Later, the anomalous genera and species were discovered to belong there too. With the desire to classify according to natural affinities ( phylogenetic affinities) the problem of classification versus distinctness arose. Polythetic characterisation seems sofar the only possibility. 

---