This article explores the concept of labour through a diremptive reading of Polish philosopher Stanisław Brzozowski’s essay “Prolegomena filozofii ‘pracy’” (“Prolegomena to a Philosophy of ‘Labour’”) written in 1909. This essay appears as a chapter in his main work Idee: wstęp do filozofii dojrzałości dziejowej (Ideas. An Introduction to the Philosophy of Historical Maturity), first published in 1910. In “Prolegomena,” Brzozowski defines labour as an inner gesture that delineates the duration of life. In the interpretation of this definition the influence of Henri Bergson on Brzozowski’s thought is stressed. Inspired by Bergson, Brzozowski understands labour as the only ground-creating—and therefore metaphysical—activity of humanity, when faced with the absence of transcendent grounds for existence in modernity. Emphasis is placed on Brzozowski’s insistence in “Prolegomena” that labour is irrational in its delineation of the absolutely new. He describes it as the α of the inner gesture of labour that cannot be known until it is performed. This unknown α is interpreted as his way of describing the groundlessness of the ground-creating activity of labour, and that this groundlessness means that labour eludes the control of the subject.