The Perception of Causal Efficacy
In many cases the causal influence may not be directly perceived. Under great emotional stress we are not inclined to introspect and observe the development of our emotions. Windelband comments at length upon the almost universal dismissal of final cause from the explanations of nature which are found in the writings of seventeenth-century philosophers. The point of the attack on occult causes was that such causes were not perceived; rather they were postulated ad hoc. Hence the all-pervading ether with which the Cartesians sought to replace the Newtonian concept of gravitation must itself be regarded as an occult cause. Of all the thinkers of the seventeenth century, Leibniz, who most clearly recognized the limits and easy beauty of materialistic explanations, gave the most careful description of causal efficacy. The events whose connections Leibniz directly experiences are those events which constitute his own life history.