Context: Arthur Schopenhauer (1788-1860) wrote that "...materialism is the philosophy of the subject who forgets to take account of himself". He claimed that an observing subject can only know material objects through the mediation of the brain and its particular organization. That is, the brain itself is the "determiner" of how material objects will be experienced or perceived:

Question: Arthur Schopenhauer lived from what year to what year?
Answer: 1788-1860

Question: What did he say that the brain would decide?
Answer: how material objects will be experienced or perceived

Question: Who wrote that "...materialism is not the philosophy of the subject who forgets to take account of himself"
Answer: Unanswerable

Question: Who claimed that a non-observing subject can only know material objects through the mediation of the brain and its particular organization?
Answer: Unanswerable

Question: Who believed the brain is not a determiner of how material objects are experienced? 
Answer: Unanswerable

Question: What does the brain not decide? 
Answer: Unanswerable

Question: What does it mean for the brain to be a non-determiner? 
Answer: Unanswerable