[Footnote 8: _Kant and Monism_. As recent German philosophy has in a large measure returned to Kant, and in some cases even deified as "infallible" the great Königsberg philosopher, it may be well here to point out once more that his system of critical philosophy is a mixture of monistic and dualistic ingredients. His critical principles of the theory of knowledge will always remain of fundamental importance: his proof that we are unable to know the essential and profoundest essence of substance, the "thing in itself" (or "the combination of matter and energy"); that our knowledge remains subjective in its nature; that it is conditioned by the organisation of our brain and sensory organs, and can therefore only deal with the phenomena which our experience of the outer world affords us. But within these "limits of human knowledge" a positive monistic knowledge of nature is still possible, in contrast to all dualistic and metaphysical fantasies. One such great fact of monistic knowledge was the mechanical cosmogony of Kant and Laplace, the "Essay on the Constitution and Mechanical Origin of the Universe, according to the Principles of Newton" (1755). In the whole field of our knowledge of inorganic nature, Kant held firmly to the monistic point of view, allowing mechanism alone as the real explanation of the phenomena. In the science of organic nature also, on the other hand, he held monism to be valid indeed, yet insufficient; here he considered it necessary to call in the aid of final as well as of efficient causes. (_Cf_. the fifth lecture of my _Natural History of Creation_ on "The Evolution-Theory of Kant and Lamarck"; also Albrecht Rau's _Kant und die Naturforschung: Eine Prüfung der Resultate des idealistischen Kritikismus durch den realistischen Kosmos_, vol. ii., 1886.) Once thus on the downgrade of dualistic teleology, Kant afterwards arrived at his untenable metaphysical views of "God, Freedom, and Immortality." It is probable that Kant would have escaped these errors if he had had a thorough anatomical and physiological training. The natural sciences were, indeed, at that time truly in their infancy. I am firmly convinced that Kant's system of critical philosophy would have turned out quite otherwise from what it was, and purely monistic, if he had had at his disposal the then unsuspected treasures of empirical natural knowledge which we now possess.]