Аннотация:Biological diversity (BD) explored by biological systematics is a complex yet organizednatural phenomenon and can be partitioned into several aspects, defined naturally with reference tovarious causal factors structuring biota. These BD aspects are studied by particular research programsbased on specific taxonomic theories (TTs). They provide, in total, a framework for comprehendingthe structure of biological systematics and its multi-aspect relations to other fields of biology. Generalprinciples of individualizing BD aspects and construing TTs as quasi-axiomatics are briefly considered.It is stressed that each TT is characterized by a specific combination of interrelated ontological andepistemological premises most adequate to the BD aspect a TT deals with. The following contemporaryresearch programs in systematics are recognized and characterized in brief: phenetic, rational (withseveral subprograms), numerical, typological (with several subprograms), biosystematic, biomorphic,phylogenetic (with several subprograms), and evo-devo. From a scientific pluralism perspective,all of these research programs, if related to naturally defined particular BD aspects, are of the samebiological and scientific significance. They elaborate “locally” natural classifications that can beunited by a generalized faceted classification.