Suppose another friend, in a provocative mood, were to ask you how you know that you are not dreaming right at this moment. What can you say? How would you prove to yourself that this is not true?

Scientific answer

1. Some of the information you have been given in your courses in
school is, inevitably, not true. How would you start to prove to
yourself that all of it is not false?
2. Suppose a friend were to challenge you, “How do you know that  2 +  2 = 4?” How would you answer?
3. Suppose another friend, in a provocative mood, were to ask you
how you know that you are not dreaming right at this moment.
What can you say? How would you prove to yourself that this is
not true?
4. Is thinking rationally always the best way to think? Is the scientific
answer to a question always the most true?