Towards a global list of accepted species I. Why taxonomists sometimes disagree, and why this matters

Taxonomy—the delimitation, naming, classification and documentation of species and other taxa—is an often-misunderstood discipline. Complex and at times contested, taxonomy occupies a sometimes discomforting intermediate position on a continuum from descriptive to hypothetico-deductive science. Two aspects of taxonomy that are striking to many observers and users are the degree to which taxonomists often disagree, and the degree of taxonomic revisionism (the replacement of one taxonomic classification with another, exemplified by the phrase ‘taxonomists are always changing the names of things’). Disagreements between taxonomists do not usually indicate taxonomic confusion or chaos, but rather often represent valid disagreements over the best, most effective and most meaningful way to interpret, describe and classify one of the most complex systems that scientists seek to describe and characterise—the patterns of variation of life on Earth. One way to partially manage disagreements among taxonomists is to develop a mechanism to synthesise the flux of taxonomic activity into agreed, broadly accepted, authoritative and scientifically robust global lists of the world’s species and other taxa. A sound understanding of some aspects of the nature of taxonomy is needed to appreciate the opportunities, complexities and limitations of the development and maintenance of such lists.