Secundum modernorum (praecipue B. Russellii) de definitione doctrinam definitio nihil aliud est quam compendium seu abbreviatio; qua de causa quaestio circa talis definitionis adaequationem (ne dicam veritatem) omnem perdidit sensum. Nos tamen, ipsam Aristotelis de definitione doctrinam pro fundamento sumentes, ostendere conamur, Aristotelico-scholasticam conceptionem, in qua definitio ut ipsae obiecti essentiae declaratio intelligitur, restitui posse. Ad hoc munus perficiendum systema quoddam logicum quod Transparens intensionalis logica dicitur adhibemus. Ita manifestatur, ne moderna quidem in logica definitionem Aristotelicam esse reiciendam. Indigentia definitionum, quorum “definiendum” non sit merum compendium propria significatione carens et brevitatis causa de novo pro “definiente” introductum, etiam ex notione “explicationis” a R. Carnapio adhibita satis clare patuit.

The modern (Russellian) theory of definition conceives definitions as abbreviations, so that the question of adequateness (let alone of truth-value) of definitions becomes meaningless. In this paper we show that beside Russellian conception of definitions understood as abbreviations, there is an Aristotelian conception, which exploits the notion of essence and that this conception can be rehabilitated from the standpoint of the modern logic (in particular by means of Pavel Tichý’s Transparent Intensional Logic). Also Carnap’s ‘explication’ indicates that what we feel to be a definition is frequently distinct from a Russellian definition.