THE MIND- STUFF THEORY. 165 



the pound. At most we can say that each ounce affects 

 it in some way which helps the advent of that move- 

 ment. And so each infra-sensible stimulus to a nerve 

 no doubt affects the nerve and heljjs the birth of sensa- 

 tion when the other stimuli come. But this affection is 

 a nerve-affection, and there is not the slightest ground for 

 supposing it to be a 'perception' unconscious of itself. 

 " A certain quantity of the cause may be a necessary con- 

 dition to the production of any of the effect," "* when the 

 latter is a mental state. 



Second Proof. In all acquired dexterities and habits, 

 secondarily automatic performances as they are called, we 

 do what originally required a chain of deliberately con- 

 scious perceptions and volitions. As the actions still keep 

 their intelligent character, iutelKgence must still preside 

 over their execution. But since our consciousness seems 

 all the while elsewhere engaged, such intelligence must 

 consist of unconscious perceptions, inferences, and volitions. 



Reply. There is more than one alternative explanation 

 in accordance with larger bodies of fact. One is that the 

 perceptions and volitions in habitual actions may be per- 

 formed consciously, only so quickly and inattentively that 

 no memory of them remains. Another is that the conscious- 

 ness of these actions exists, but is split-off from the rest of 

 the consciousness of the hemispheres. We shall find in 

 Chapter X numerous proofs of the reality of this split-oft' 

 condition of portions of consciousness. Since in man the 

 hemispheres indubitably co-operate in these secondarily 

 automatic acts, it will not do to say either that they occur 

 without consciousness or that their consciousness is that of 

 the lower centres, which we knoAv nothing about. But 

 either lack of memory or split-off cortical consciousness 

 will certainly account for all of the facts.f 



Third Proof. Thinking of A, we presently find our- 

 selves thinking of C. Now B is the natural logical link 

 between A and C, but we have no consciousness of having 

 thought of B. It must have been in our mind ' wwcon- 



* J. S. Mill, Exam, of Hamilton, chap. xv. 

 f Cf. Dugald Stewart, Elements, chap. ii. 



