"You are entitled to your own opinion. You're not entitled to your own facts." Attributed to Daniel Patrick Moynihan, or James R. Schlesinger. This is often flung about when debating matters of faith versus matters of science.
What are facts? Can science provide us with facts? (a bee beats its wings 200 times per second). What about history? (Thomas Jefferson was born on April 13, 1743). Do facts change? Are somethings we think are fact later found out to be not facts? What if a fact is false? Is it no longer a fact? Does fact imply truth?
To say that "human beings are complex creatures" is that a fact or an opinion?