Faith is a polarizing word in my circles. Depending on what side one comes down on regarding the existence of God, people have biased meanings for the concept. I know atheists who define it as “belief in something contrary to evidence” and theists who define it as “justified, true belief.” A working definition of faith for which I’ve had the most luck in finding agreement is “belief in something beyond what the evidence warrants.” Let’s plug this common term of “faith” into a few use cases for the word.
“I have faith that my wife will never cheat on me.” I think this works. My wife has never cheated on me in the past (as far as I know) and has never behaved in such a way that I think she would consider cheating. That said, I know relationship data shows that cheating is common. So in this case, I have a decent amount of evidence in the form of past experience that justifies a belief that she probably won’t cheat in the future, but a realist should still consider that it could happen more than I actually consider it. I’m willing to admit that I have faith in my wife’s fidelity. Thankfully, I don’t need as much faith as I would if I was aware that she cheated in the past.
“I have faith that the sun will rise in the morning.” I don’t think this is a good use of the term faith, even if the statement is understandable and technically accurate. Like the example with my wife, I have evidence in the form of past experience that the sun rises every morning. Not just decent evidence, but a perfect record of the sun rising every morning. One could argue that “morning” is defined by the sun rising. Depending on location and season, we can track exactly when sunrise will be and confirm that that fiery ball in the sky sticks to the schedule. Beyond personal experience, I know enough about astronomy to explain orbits and gravity so...faith doesn’t really come into play here. It is possible that the sun does not rise tomorrow at our expected time? Yes, but only if some catastrophic event with statistically insignificant odds--like earth being knocked off its axis--happens. To use the term more correctly, I have faith that some observatory or news outlet would give me notice before the night before such an event could occur.
“I have faith that God exists.” Okay, I don’t, but if I did, this is the best use case for the word so far. Even if we grant theists that there is some evidence for God’s existence, you know that I’d argue that it isn’t very good evidence. And since most religion requires belief to the degree of certainty, or at least an attempt for such belief, faith is what gets them the rest of the way from the perceived evidence available.
So is faith good or bad? It depends. The faith in my wife means that I don’t easily get jealous which is a positive in my relationship. However, that is but a bit of faith. If my wife cheated regularly or otherwise treated me poorly, having faith that tomorrow will be different would be a negative force for my well being. Faith can be good in small amounts, but should generally be avoided. Strive to have your beliefs reflect the evidence to the degree it merits and not far beyond, if any.