28. Ideas of David Hartley and Joseph Priestley Hartley Ideas give direction to the development of associative British empirical psychology. His credo he expresses with sufficient clarity: "Everything is explained primary sensations and laws of the association." Hartley elevated association of universal mechanical law of all forms of mental activity, something similar to the great Newton's law of universal gravitation. In his book "Reflections on the man, his structure, his duty and hopes" Hartley argued that the psychic world of man develops gradually as a result of complications of primary sensory elements by virtue of their association in the adjacency of these elements in time and frequency of repetitions combinations thereof. With regard to general concepts, they occur when a sound from the association, which remains unchanged in various conditions, eliminating all accidental and insignificant. The totality of these relations is held constant as a whole because of the word, which acts as a generalization factor.