62 CEREBRAL FORCES. [i. 



conceptions raises the questions^ whether the external sensations 

 and their sentient actions depend solely on the body ; whether 

 the sensational perceptions, stimuli, desires, aversions, instincts, 

 and passions, with their sentient actions, depend partly on the 

 body, and partly on the mind; and whether the intellectual 

 conceptions, motives, the will, and the unwill, together with 

 their actions, depend solely on the mind. Indeed, properly, 

 all sentient actions are produced by the cerebral forces excited 

 into action by the conceptions, but while the mind produces 

 all its conceptions in virtue of its conceptive force, they again 

 are dependent on the material ideas in the brain (25), and 

 consequently on sentient actions (97), as is fully shown in 

 metaphysics. (Vide § 119, and Baumgarten^s 'Metaphysics,^ 

 §§ 563, 567.) 



Action of the Material Ideas in the Nervous System. 



113. We have hitherto followed the arrangement laid down 

 in § 30, and shown how material ideas are produced in the brain, 

 namely, partly by external impressions on the nerves (through 

 external sensations), which are propagated to the brain (31 — 64) 

 partly by the influence of the conceptions which the mind, 

 by its own power, produces in the brain (65 — 112). There is 

 now another question to answer, namely, what functions do 

 the material ideas perform in the economy? In this chapter, 

 according to § 16, we can only consider them in their relations 

 to the animal machines — the brain and nerves — leaving out 

 any reference to the mechanical machines. 



114. The material ideas are animal forces, in so far as they 

 manifest their operations in the economy. Now since they 

 act in accord with the mind (97), they are also animal-sentient 

 forces (6). 



115. All material ideas are solely and exclusively in the 

 brain (25). Consequently, they produce their eff*ects either 

 directly through the brain, or indirectly through the nerves, by 

 means of which the brain is extended through the entire 

 animal body (12, 13) ; because the nerves are the only animal 

 machines in those animals which possess true conceptions (9); 

 but the vital spirits are only the means by which they perform 

 their functions (17, 18). 



