FROM the dawn of philosophical inquiry and right on down to modern times the relationship between the knower and the known has posed a perennial problem. Ancient Greek thought, for the most part, as well as later Christian thought agreed that within the one who observes the passing events of the world there exists a reality different in kind from the objects of observation. This reality or entity was commonly designated mind and that which it reports to the mind-ful, or thinking, subject was called matter. If matter and mind thus differ in basic nature, a secondary difficulty must be met: how to explain or account for their interaction? How can mind or thinking substance know matter or extended substance? What is the relation between thought and things?
The variety of answers constitutes the variety of philosophic systems. Dualistic systems accept the separateness of matter and mind; they differ either in denying any interoperation between them, or in accounting for interaction by varying theories. Monistic philosophies, on the other hand, dispose of the problem either by erasing one of the terms-Materialism disposing of mind and asserting that nature is the whole of reality; Idealism disposing of matter and maintaining that spirit is all-or by fusing the terms into a single entity, a reductive device resolving in Pantheism, where mind and matter coalesce in a single infinite substance.
The eighteenth century, known as the Age of Reason, or the Enlightenment, saw the rise of the new science whose prophet was Isaac Newton, and of the eventually dominant empirical philosophy of John Locke. In every field of physical and metaphysical inquiry the Masters advocated and demonstrated the complete freedom, even to the total repudiation of authority in the areas of conduct and belief. The empiricists attacked traditional doctrine, particularly in religion, morality and politics, and offered by way of an approved substitute a theology rationalized into Deism and stripped of revelation and miracle and ritual. Reason ruled, protesting that what was unrational was necessarily irrational; proffering rational solutions to all problems, in the prac