The ideal of mathematical exactness is strongly paradigmatic for modern science, for which Mathematics practically functions as a metaphysical foundation. This strongly influenced Philosophy. In our century, however, critical voices arise, even from the ranks of scientists. Reflection on the foundations of Mathematics has produced a deeper insight into its nature. The tendency to judge content by structure becomes less predominant. Metaphysics is no longer rejected as only producing constructions with unjustified claims to necessity. This book combines contemporary Philosophy of Mathematics with classical philosophical themes. It replaces the anti-metaphysical tendencies of modern and postmodern Philosophy by an unrestricted horizon of epistemic perspectives.