Posted for Marc Van Regenmortel:
In his welcome admission that viral metagenomic sequences are not viruses, Adrian Gibbs once more states that virus species are not "constructions of the mind " but are groups of indeterminate numbers of material viral objects. He refuses to admit that all hierarchical biological classifications are made up of concepts called classes (hence the term classification) and of taxa (hence taxonomy). In virology, the lowest rank (another concept) is the species which has real members that are viruses and these viruses are also members of certain higher taxa such as genera, families and orders. This phenomenon of class inclusions is a peculiarity of hierarchical classifications which obviates the need to repeat the additional properties that a member of a species acquires by virtue of also being a member of a genus or a family (because of the existence of genus-defining and family-defining properties). Higher taxa also correspond to mental categories that overlap rather than being individual, similar material objects and all the members of every l taxon are actually also viruses. It is strange that certain virologists view species not as classes but as groups of similar material objects that share a common physical property while they accept that higher taxa are conceptual constructions of the human mind.
The ICTV classifies virus species on the basis of phenotypic, biological and relational properties of viruses and these arise from the interactions of viruses with their hosts and vectors . In the case of viral metagenomic sequences, these relational properties are nearly always unknown which is the reason why it is usually not possible to incorporate such sequences in the list of ICTV virus species.
Confusing a concept such as a class, a taxon or a rank with an object is one of the most common logical fallacies, called reification (from the Latin res for a thing), which consists in viewing a thought, an idea or a concept as if it were an object. Although the concept of virus species can be viewed as a class, a taxon or a rank, it should not be confused with a real , material object. The same is true of all the other hierarchical taxa that have increasing numbers of virus members, the higher the taxon, but which remain nevertheless also conceptual creations of taxonomists.