100300
‘ The problem of demarcation ’ is an expression introduced by Karl Popper to refer to ‘ the problem of finding a criterion which would enable us to distinguish between the empirical sciences on the one hand , and mathematics and logic as well as " metaphysical " systems on the other ’ .
 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