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One of Aristotle ’s early interests lay in the classification of the natural world , how for example the genus " animal " could be first divided into " two-footed animal " and then into " wingless , two-footed animal " .
 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:
 Aristotle