440 THE ANIMAL FUNCTIONS. [ch. v. 



The mind perceives the external impressions made on the 

 nerves, and communicated to the sensorium commune, by 

 acquiring certain notions and images of them termed ideas.^ 

 These differ according as they are brought from the various 

 organs of the senses to the sensorium commune, for vision excites 

 one kind of ideas in the mind, hearing another kind, taste, 

 smell, and touch other kinds. Ideas also differ in their degree of 

 vividness, for the more vivid ideas presuppose a more impres- 

 sible nervous system, that many impressions are not commu- 

 nicated at the same time to the sensorium, (for the mind clearly 

 perceives one idea after another,) or an impression more powerful, 

 repeated, continuing longer, or new and unusual. 



Whilst engaged in the examination of ideas, the mind judges 

 whether there be discrepancy or agreement amongst them, 

 whether they be new or often-repeated ideas — whether they 

 threaten anything injurious to our body, or promise anything 

 beneficial. When engaged in this judgment, the mind must 

 remember the idea first perceived, when it compares it with 

 another for the purpose of seeing their agreement or discrepancy, 

 and consequently the faculty of judging presupposes memory. 

 If many compound ideas be compared one with another, a 

 compound judgment is made, and this is termed reasoning. 



The mind wills, when it endeavours to retain or remove that 

 which by the ideas is understood to be good or evil. 



It imagines, when the ideas of things formerly present but 

 now absent are excited, voluntarily or involuntarily, either 

 from some internal disposition of the brain, or from some 

 similar or associated idea excited in the mind. Those ideas 



• I do not here treat of the hypotheses as to the formation of ideas in perception 

 and imagination, whether they be impressions traced on the brain, which Haller 

 defends in his ' Elem. Phys.,' torn, v, p. 541, &c. ; or whether they are a certain 

 motion and minute vibrations or oscillations, which, being different, are suitable to 

 the excitation of different ideas, as Bonnet ingeniously supposes. (See his ' Analy- 

 tischer Versuch uber die Seelenkrafte.') Reimarus (see Gbttingen Magazine for the 

 past year, part vi,) strongly disapproves of the doctrine, that there are material 

 tracings of the ideas impressed on the brain, since the memory being lost in disease 

 could never be restored, as it often is, if, indeed, the tracings of the ideas, once 

 obliterated, cannot be restored when the disease terminates, with the same facility 

 as the fibres of the brain can be re-excited into similar oscillations on the oppor- 

 tunity being afforded; and because, as the traces are always present, there could 

 be no reason why the representation of ideas should cease during profound sleep. 

 In this matter those more acute than I will decide. 



