Phenetic classification does not depend on any knowledge or hypothesis of phylogeny. Phenetic classification presumes that the organisms, when adequately measured, will tell us how they should be classified. Phenetic classification thus does not concern itself with naturalness. But in practice it remains necessary to choose which and how many characters to measure. Furthermore, there has been no agreement on which statistical tools should be used to identify groupings.
Phylogenetic classification uses inferred phylogenetic relations.
The term cladistics is based on the term clade , a synonym for monophyletic group , defined as the entire set of species descended from a common ancestor. In cladistics, there is one true classification which is based upon the objective, natural reality of phylogeny. Unfortunately, since phylogeny itself remains largely unknown, so does the basis for cladistic classification. Phylogenetic systematics must therefore be carried out by inferring phylogeny. But once we have a cladistic classification, we also have a hypothesis of phylogeny.