THE MIND- STUFF THEORY. 157 



On this supposition tliere are no unperceived units of 

 mind-stuff preceding and composing the full consciousness. 

 The latter is itself an immediate psychic fact and bears 

 an immediate relation to the neural state which is its un- 

 conditional accompaniment. Did each neural shock give 

 rise to its own psychic shock, and the psychic shocks then 

 combine, it would be impossible to understand why sever- 

 ing one part of the central nervous system from another 

 should break up the integrity of the consciousness. The 

 cut has nothing to do with the psychic world. The atoms 

 of mind-stuff ought to float off from the nerve-matter on 

 either side of it, and come together over it and fuse, just 

 as well as if it had not been made. We know, however, 

 that they do not ; that severance of the paths of conduction 

 between a man's left auditory centre or optical centre and 

 the rest of his cortex will sever all communication between 

 the words which he hears or sees written and the rest of 

 his ideas. 



Moreover, if feelings can mix into a tertium quid, why 

 do we not take a feeling of greenness and a feeling of red- 

 ness, and make a feeling of yellowness out of them ? Why 

 has optics neglected the open road to truth, and wasted 

 centuries in disputing about theories of color-composition 

 which two minutes of introspection would have settled 

 forever ? * We cannot mix feelings as such, though we may 

 mix the objects we feel, and from their mixture get new 

 feelings. We cannot even (as we shall later see) have two 

 feelings in our mind at once. At most we can compare 

 together objects previously presented to us in distinct feel- 

 ings ; but then we find each object stubbornly maintaining 



bine ' into the tertium quid of feeling, yellow. What really occurs is no 

 doubt that a third kind of nerve-process is set up when the combined lights 

 impinge on the retina, — not simply the process of red plus the process of 

 green, but something quite different from both or either. Of course, then, 

 there are no feelings, either of red or of green, present to the mind at all ; 

 but the feeling of yellow which w there, answers as directly to the nerve- 

 process which momentarilj' then exists, as the feelings of green and red 

 would answer to their respective nerve-processes did the latter happen to be 

 taking place. 



* Cf. Mill's Logic, book vi. chap. iv. § 3. 



