Jacobi questioned the concept of thing-in-itself. In his words, Kant's philosophy is inconceivable without it, with it, it is unacceptable. Presumably 'Dinge-an-sich' affect our sense through phenomena. But even if they act indirectly, they affect us, and therefore enter in some inscrutable causal relation with our senses. That conclusion cannot be accepted, as causality is a category of the intellect and belongs to the phenomena, and if the 'noumena' were to acquire that power they would be indistinguishable from them. It is possible to defend Kant against this criticism, says the author, and quotes appropriate passages from the 'Critique of Pure Reason'. The question remains, however, if this rebuttal offers a conclusive argument or is merely a verbal response to Jacobi's objections. It is interesting to note that some authors in contemporary philosophy are engaged in a similar controversy. For instance, when Michael Dummet tries to give a purely semantic interpretation of epistemology, he avoids using such phrases as 'the reality existing independently of us', but he is unable to refrain entirely from such constructions. He refers to objective reality, while trying never to mention its name.