Final answer:
John believes people must endure sorrow to appreciate joy, but whether one agrees or disagrees can vary based on personal beliefs and experiences.
Step-by-step explanation:
John believes that people must endure sorrow in order to appreciate joy. Whether or not someone agrees or disagrees with John's viewpoint can depend on their personal beliefs and experiences. Some people may argue that experiencing sorrow can help individuals develop empathy, resilience, and a greater appreciation for positive experiences. Others may disagree and believe that one can appreciate joy without having to go through suffering. It's important to remember that everyone may have different perspectives on this matter.