Hardest crossword puzzle eva! -Celina-

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Across
  1. 4. Surname of a famous philosopher
  2. 6. A way of thinking to understand the world
  3. 7. Money industry
  4. 8. Using our senses to check
  5. 9. To be happy
Down
  1. 1. You were a blank slate
  2. 2. A way of testing our hypothesis
  3. 3. Collection of knowledge
  4. 5. Logical sense of our brain to explain something