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Since the time of Plato and Aristotle , some philosophers have posited true reality as " timeless " , based on permanent substances , while processes are denied or subordinated to timeless substances .
 Plato, Aristotle
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Plato, Aristotle