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The term " possible world " goes back to Leibniz 's theory of possible worlds , used to analyse necessity , possibility , and similar modal notions .
 person: Leibniz
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Leibniz