In the presentation I will analyse Kant’s conception of modalities and consider its relevance to his critical metaphysics. With his Tables of Judgements and of Categories Kant makes an important division between two kinds of modality, of which the former is only logical and the latter transcendental, i.e., objective. Only judgements that are necessary in both ways are properly metaphysical. This distinction is important for Kant’s distinction between Transcendental Analytic and Transcendental Dialectic, i.e., between acceptable and unacceptable metaphysics. I submit that not only is Kant’s theory of modality useful for properly understanding his arguments in the Dialectic, but that only by distinguishing between the two types of modality can one can make sense of his theory that the ideas of reason are simultaneously inevitable and erroneous. This modal analysis thus offers a new and important point of view to Kant’s metaphysics and its critique.