6280
495 BC ) and the Pythagoreans , Empedocles challenged the practice of animal sacrifice and killing animals for food .
 Pythagoreans, Empedocles
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Pythagoreans, Empedocles