This post is largely inspired by my reading of A Faith Brief: A Lawyer’s Argument for Why Faith Prevails Over Doubt by Patrick M Garry, although I am unlikely to use quotes from the book for this. I was reading through it and adding commentary a bit over a year ago, but I stopped bothering with the commentary about halfway through when the author revealed that he is a creationist. Apparently evolution is worthy of doubt, but the Bible is not.
Essentially, the book claims that faith is superior to doubt, that doubt blinds us and faith opens our eyes. Faith is better, as it is a gift from God.
The most immediate problem is that god has denied some of us that gift. Some of us are quite incapable of believing without a certain burden of proof being met, and god has certainly refused to offer that proof.
If you would argue, as does the author of that book, that faith is the default position, not doubt, I must ask: What is your justification for doubting Allah, Thor, Zeus, Horus, Marduk, Shiva, Zoroaster, Pangu, Buddha, and the Flying Spaghetti Monster? You must have a justification for doubting the existence and/or teachings of each and every deity and/or guru ever, if doubt is not the default position. You also have to have justification for doubting the prophets of the future who disagree with your faith, as well as the deity myths that will be thought up by future generations, if any. Otherwise, doubt IS the default position, and the burden of proof is on you to make the case for why we should not doubt.
This is why faith is not valuable: it does not reliably lead to conclusions. If your only reason for believing something is “I have faith”, what prevents you from accepting that eating poison ivy cures cancer based on faith? What right do you have to say anyone else is wrong when they say “but I have faith”, if you believe anything on faith? What if two people believe contradictory things, both based on faith? How can anyone possibly just between them?
By contrast, consider what happens when two people with conclusions based on evidence and reason disagree: they each present their evidence and reasons. Sometimes, they will even do their best to point out flaws in the reasoning of the other person. You can see which side has stronger evidence, which side has reasoning with fewer flaws. You can look for fallacies. You might even be able to repeat experiments they have performed.
Faith just has nothing in comparison. It is worthless as a method for discovering truth.
Indeed, it is worse than useless, because it encourages gullibility. If you don’t rely on empirical evidence but only on faith, you may end up wasting thousands of dollars on a cure for cancer and dying in greater pain sooner than if you had sought out the proven medical treatments.