208 Phllosophij of the Human Mind. [Chap. XIL 



to expect a state of consciousness or enjoyment 

 hereafter is derived from the scripture doctrine 

 of the resurrection. In former parts of this work 

 the services of Dr. Priestley in the physical sci- 

 ences have been mentioned witli high respect, and 

 with frequently repeated tributes of applause. It 

 is to be re2:retted that so much of what he has 

 written on the philosophy of mind, and almost the 

 whole of his writings on the subject of theology, 

 should be so radically erroneous, and so subversive 

 of all the interests of evangelical truth and prac- 

 tical piety. 



The principal materialists of the eighteenth cen- 

 tury differed in some of the details of their opini- 

 ons from those philosophers of preceding times 

 who held the same general doctrine. Epicurus 

 supposed the soul of man to be a material sub- 

 stance, but a very refined and attenuated kind of 

 matter. He taught that this substance, notv/ith- 

 standing the extreme subtlety of its texture, is 

 composed of four distinct parts ; fre, which causes 

 animal heat ; an ethereal principle, which is moist 

 vapour; air; and a fourth principle, M'hich is the 

 cause of aen.^Mt ion. This sentient principle he sup- 

 posed to dilfer essentially from the* three former, 

 biit to be, like the re*t, corporeal, because it is 

 capable both of acting and being acted upon by , 

 bodies. From the union of the soul, thus con- 

 stituted, with the body, he believed life and sensa- 

 tion to result. Something like this seems to have 

 been the opinion of almost all the ancient mate- 

 rialists. Spinoza and llobbes held a system of ma- 

 terialism quite as gross as any of their predeces- 

 sors y for ihey seem to have thought that cveri^ 



