The subject of this article is a method of jurisprudential definition introduced by a British philosopher and jurist H.L.A. Hart. In particular it discusses: (1) the author’s account of specificity of legal discourse (meaning and speech function of legal concepts) and discrepancy between that and a traditional method of definition per genus et differentiam; (2) Hart’s alternative method of “philosophical definition” of legal concepts; (3) correlation of this method with other definitive / explanatory techniques used by the author in 1949–1961 papers and further; (4) complexities of jurisprudential and philosophical character related to Hart’s method. Special attention is paid to Hart’s position as to relationship between semantics and pragmatics in legal discourse (and so in “philosophical definition”). The conclusion is established claiming a change of the author’s corresponding views: a transition to a looser type of connection between meaning and force of legal concepts in which these concepts (while maintaining its social, institutional character) can be used both in descriptive (“external”) and “ascriptive” / normative (“internal”) statements.