Source, in full
The more I think about myself, the more I’m persuaded that, as a person, I really don’t exist. That is one of the reasons why I can’t believe in any orthodox religion: I cannot believe in my own soul. No, I am a chemical compound, conditioned by environment and education. My "character" is simply a repertoire of acquired tricks, my conversation a repertoire of adaptations and echoes, my "feelings" are dictated by purely physical, external stimuli.
Notes from Wikiquote
Christopher did well to call himself woolly-minded. All he has actually stated here is that he can’t believe in his own individuality as something absolute and eternal; the word "soul" is introduced, quite improperly, as a synonym for "person." | Ch. 15, p. 306