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The use of " physical " in physicalism is a philosophical concept and can be distinguished from alternative definitions found in the literature ( e.g. Karl Popper defined a physical proposition to be one which can at least in theory be denied by observation Since any change in a combination of properties must consist of a change in at least one component property , we see that the combination does indeed supervene on the individual properties .
 Karl Popper
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Karl Popper