Leszek Nowak . Key words: unitary metaphysics, method of paraphrase, substance. This work is not a historical piece. It applies Ajdukiewicz's method of paraphrase (1937) to a basic metaphysical notion, the notion of substance. It aims at finding constructs which can be admitted as equivalents (quasi-translations) of the three notions of substance (the Aristotelian, the Cartesian and that elaborated by Spinoza) in the universe of unitary metaphysics. The author also endeavors to compare explanatory efficiency of those paraphrases under the assumption of unitary metaphysics.