Velasco recently criticized our formal definition of the species concept, arguing for its inappropriateness both in fundamental and practical aspects [Velasco JD (2008) Biological Journal of the Linnean Society, 93, 865-869]. Here, we clarify some misunderstandings that are at the basis of Velasco's paper. First, we show why and how the definition of the species concept can be grounded in the theory of evolution and what that implies. Then, we explain why Velasco's formal criticisms are unjustified. Finally, we point out the practical and methodological consequences of a rigorous conceptual framework for species study, and we show that today's development of species delimitation methods fully agrees with our proposal.