CH.iv.] RELATION OF CEREBRAL & NERVE FORCES. 305 



rms animal acts, it must necessarily therefore be endowed with 

 cerebral forces, or with a soul, or with will ; for it is undeniably- 

 possible, that the vis nervosa alone can cause the greater num- 

 ber of the animal acts (590). The majority of philosophers 

 have been led by this error to consider all animals without 

 exception as endowed with souls ; but it is highly probable, that 

 many have neither consciousness nor feeling. 



595. It cannot be correctly inferred, that, because in a 

 sensitive or thinking animal, movement is excited in virtue of 

 irritability, or by the vis nervosa of external impressions gene- 

 rally, it cannot be a sentient action of the external sensation 

 caused by the impression ; or, vice versa, that because it is a 

 sentient action of the external sensation of an external im- 

 pression, it cannot be a nerve- action of the impression only. 

 The first is the error of some recent writers, who, since Haller 

 recognised the agency of the vis nervosa of external impressions 

 in exciting direct nerve-actions, and taught it under the term 

 irritability, wished to maintain, that all animal movements not 

 resulting from volition are dependent on irritability, and 

 erroneously deny those dependent on sensation. The latter 

 error is that of the Stahlians, when they maintain, that in ex- 

 ternal sensations the body is purely passive, and does not co- 

 operate by means of its own proper forces. 



596. It cannot be correctly inferred, that because in a 

 sensitive or thinking animal the movements which accompany 

 the sensational conceptions, incitements, desires, aversions, &c., 

 are sentient actions, for this reason they cannot be nerve- 

 actions j and vice versa, that they cannot be sentient actions of 

 these sensational conceptions (592). From this error, taken in 

 connection with the second mentioned in the preceding para- 

 graph, the old error has probably arisen, and which the author 

 of the article '^Sensibilite,^^ in the 'Dictionnaire Encyclopedique' 

 has lately reproduced, namely, that there are two kinds of souls 

 in reasoning animals, the one being the rational soul, by which, 

 sentient actions are developed according to psychological laws; 

 and the other a sensational soul, by which the sentient actions 

 of the external sensations and other sensational conceptions are 

 developed according to the laws of the vis nervosa. We have 

 shown, however, that to the action of the latter no soul is 

 necessary. 



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