10. No data or conclusion is unchallengeable or unchangeable.
Repeat again: "I can be wrong." Yes, absolutely anything can - and should be - questioned. To not do so, in fact, is irresponsible.
An important extension of this: anyone can be wrong. That includes your parents, teachers, the government, religious leaders, scientists, "experts", books, newspapers, TV, the internet - everyone. You should question all data and conclusions rigorously, regardless of the source.
The concept of faith is exactly this: believing something without any real supporting data. Faith is very important to many people, and can often closely tie in with that same function of our brain that generates hunches. Without any logical reason, the emotional part of ourselves may guide us to believe something anyway - often very strongly.
Like hunches, faith can be a very good thing. It can be an important part of getting in touch with one's spiritual side. We might have faith in a child's ability to succeed at school or some other important endeavor, helping them to actually achieve that goal. We might also have faith in a loved one's ability to fight a difficult disease, giving them the love and support they need whether or not they win the battle. Faith is a powerful component of human existence and becoming a critical thinker does not mean giving it up.
Faith, however, must be tempered by reality. Think of the places where faith can be harmful: if we are pushing a child to be at the top of their class even though they have a learning disability like dyslexia, our insistence might result in the child feeling bad about themselves when they don't achieve that unreasonable expectation. Insistence on a loved one's survival even when it is clear that they are near the end may cause us to not cherish the remaining time that we have with them, or to fail to be emotionally prepared when they do pass away.
If someone ever claims that they or their statements cannot be questioned, this should set off a truckload of alarms. The worst arguments evaporate under scrutiny. The best arguments weather even the toughest inquiry and come out the other side rock-solid, stronger than ever. So if someone is afraid of their arguments being questioned...
Although it appears in all aspects of human life, faith is most commonly associated with religion. This is a complex and challenging subject which I don't want to get into here. Suffice it to say that it is possible to have strong faith, but still apply critical thinking to some aspects of your religion. I would assert that Martin Luther was one of the most notable critical thinkers in history, precisely because he applied it to his religion, and thereby spawning the modern age of Christian belief. The result of his application of critical thinking was stronger faith and a deeper connection to his spirituality. (Disclaimer: your results may vary)