The paper is an attempt to explain what a transcendental argument is for Kant. The interpretation is based on a reading of the 'Discipline of Pure Reason', Sections 1 and 4 of the first Critique. The author first identifies several statements that Kant makes about the method of proof he followed in the 'Analytic of Principles' which seem to be inconsistent. He then tries to remove the apparent inconsistencies by focusing on the idea of instantiation and drawing a distinction between (...) the intension and the extension of a concept. Finally, the results are applied to the second 'Analogy of Experience' for the purposes of illustration. The paper should be seen as an attempt to provide an historical answer to a question that has been treated thematically in much of the recent literature. (shrink)