The significance of Kant's philosophy reaches down into our own time. Not only have the theories of philosophers of a variety of schools been determined by Kant; scientists, too, have employed his philosophy in carrying out philosophical criticism of scientific theories or setting up systems of natural philosophy. No one who wishes to attain an understanding of present-day philosophical thinking can ignore his great influence. It is equally in evidence where scientists have attempted to perpetuate Kant's ideas by adapting them to the changes in science — as Helmholtz did with respect to geometry — and where they have totally rejected Kant's ideas precisely as a means of contrasting them with their own philosophical conceptions — as Mach did in his critique of the concept of the thing-in-itself. Thus Kantian philosophy does not only live today in the neo-Kantian system of thought, in the so-called Marburg school, which over the past fifty years has recreated a group of Kantians in the strict sense. Kant's ideas are to be found in other schools of philosophy as well, although some of these — the phenomenologists, for instance — place less emphasis on their connection with Kant. This sweeping influence does not apply only to German philosophy. Philosophers of other countries have also taken up positions for or against Kant in their basic writings, thus acknowledging his place as a cornerstone of philosophical thinking.