vi] Sylvius and his Pupils. 169 



phenomena of a machine governed by ordinary physical laws ; 

 had chemistry been as advanced in Descartes' time as in Stahl's 

 he might have added chemical laws. To Stahl on the contrary 

 a machine was exactly that which the animal body was not ; 

 its phenomena were not the phenomena governed by physical 

 and chemical laws, but phenomena obeying laws of a wholly 

 different kind, the laws of the sensitive soul ; the sensitive soul 

 made itself felt in even the simplest and so to say lowest 

 changes of the body. 



With van Helmont, Stahl had much more kinship, and 

 indeed his views may to a certain extent be regarded as a 

 development of van Helmont's ; the sensitive soul of Stahl is 

 that of van Helmont with two differences only. The sensitive 

 soul of Stahl works directly on chemical processes, without the 

 intervention of archaei, and is not a mortal something associated 

 with, and as it were the shell of an immortal mind, but it is 

 itself the immortal principle, spiritual and immaterial, coming 

 from afar, and at the death of the body returning to whence it 

 came. 



Stahl's fundamental position is that between living things, 

 so long as they are alive, however simple, and non-living things, 

 however composite, however complex in their phenomena, there 

 is a great gulf fixed. The former, so long as they are alive, are 

 actuated by an immaterial agent, the sensitive soul, the latter 

 are not. This position he dev elopes at great length in his 

 treatise, De mixti et vivi corporis vera diversitate, ' On the real 

 difference between a chemical compound and a living body/ 



A living body is distinguished from a non-living merely 

 compound body by the fact that though capable of change and 

 indeed, in the very development of its activity, continually 

 undergoing changes, it nevertheless maintains for a given period 

 an identical existence. 



" This very preservation of a thing essentially destructible 

 " by which its destruction through its own activity is prevented 

 " is exactly that which we ought to understand by the common 

 " word ' vital.' This is the feature by the absence of which a 

 " body so far as it is simply a compound body contrasts with and 

 " is distinguished from a body which is living." 



