D'ALEMBERT. 495 



ball, are retained in their vast orbits by the same power which 

 causes a stone to fall to the ground; that this power, with 

 their various motions, moulds those bodies into the forms 

 they have assumed; that their motions and the arrangement 

 of their paths cause their mutual action to operate in such a 

 manner, as to make their courses constantly vary, but also to 

 prevent them from ever deviating beyond a certain point, and 

 that the deviation being governed by fixed rules, never can 

 exceed in any direction a certain amount, so as to preserve 

 the perpetual duration of the system; such truths as these 

 transport the mind with amazement, and fill it with a pure 

 and unwearying delight. This is the first and most legitimate 

 pleasure of philosophy. As much and the like pleasure is 

 afforded by contemplating the truths of Moral Science. To 

 trace the connexion of the mental faculties with each other; 

 to mark how they are strengthened or enfeebled; to observe 

 their variety or resemblance in different individuals ; to ascer- 

 tain their influence on the bodily functions, and the influence 

 of the body upon them; to compare the human with the 

 brute mind; to pursue the various forms of animal instinct; 

 to examine the limits of instinct and reason in all tribes; 

 these are the sources of as pleasing contemplation as any 

 which the truths of abstract or of physical science can bestow; 

 from these contemplations we reap a gratification unalloyed 

 with any pain, and removed far above all risk of the satiety 

 and disgust to which the grosser indulgences of sense are 

 subject. But the study of Political Science is equally fertile 

 in the materials of pleasing contemplation. The examination 

 of those principles which bind men together in communities, 

 and enable them to exercise their whole mental powers in 

 the most effectual and worthy manner ; the knowledge of the 

 means by which their happiness can be best secured and 

 their virtues most promoted ; the examination of the various 

 forms in which the social system is found to exist ; the 

 tracing all the modifications which the general principles of 

 ethics and of polity undergo in every variety of circumstances, 

 both physical and moral ; the discovery of resemblances in 

 cases where nothing but contrasts might be expected; the 

 observation of the effects produced by the diversities of poli- 



