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According to philosopher Steven Crowell , defining existentialism has been relatively difficult , and he argues that it is better understood as a general approach used to reject certain systematic philosophies rather than as a systematic philosophy itself .
 Steven Crowell
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Steven Crowell