(Observation on Man, 1749). The physiological correlate of association is the combination of various oscillations of particles of the brain. The significance of association manifests itself in three specific forms: it is possible for ideas to so unite internally as to form a new idea with new attributes; conscious activities may, by repetition, be performed entirely automatically; the vividness of an idea may be transferred to the idea which is associated with it. Consciousness can assume an entirely different character from its original by means of these three processes. The most radical metamorphoses become possible in this way, as e. g. when an egoist lapses into complete mystical self-forgetfulness through a series of degrees.—These theories were popularized through the writings of Joseph Priestley(1733-1804), the noted chemist. And Erasmus Darwin(1731-1802) afterwards went a step farther, and proposed the hypothesis of the transmissibility of such acquired characters (Zoonomia, 1794).
Hume was opposed by what has been called, in the narrower sense, the Scottish School. These thinkers aim to quit theorizing and return to the mere description of mental phenomena. As against the results of analytical philosophy they appeal to common sense. Thomas Reid(1710-1796), Professor at Aberdeen and Glasgow, is the most famous representative of this school. His most important work, Inquiry into the Human Mind on the Principles of Common Sense(1764), was written against Hume, whom he regarded as the destroyer of all science, religion and virtue.
According to Reid, there are certain instinctive presuppositions at the basis of all knowledge, which are unassailable by doubt. These principles of common sense are older than philosophy and proceed from the
