challenge: What is the main difference between possibilianism and agnosticism, according to David Eagleman's definition?
  
  A. Possibilianism is a form of traditional theism, while agnosticism is a form of atheism
  B. Possibilianism involves an active exploration of novel possibilities, whereas agnosticism is a more passive acceptance of uncertainty
  C. Possibilianism is a form of certainty, while agnosticism is a form of doubt
  D. Possibilianism is based on scientific evidence, while agnosticism is based on faith
  Answer: 