The Buddha gave us several teachings on facing uncertainty.
“Bhāradvāja, first you took your stand on faith, now you speak of oral tradition. There are five things, Bhāradvāja, that may turn out in two different ways here and now. What five? Faith, approval, oral tradition, reasoned cogitation, and reflective acceptance of a view. These five things may turn out in two different ways here and now. Now something may be fully accepted out of faith, yet it may be empty, hollow, and false; but something else may not be fully accepted out of faith, yet it may be factual, true, and unmistaken. Again, something may be fully approved of…well transmitted…well cogitated…well reflected upon, yet it may be empty, hollow, and false; but something else may not be well reflected upon, yet it may be factual, true, and unmistaken. Under these conditions it is not proper for a wise man who preserves truth to come to the definite conclusion: ‘Only this is true, anything else is wrong.’”
“But, Master Gotama, in what way is there the preservation of truth? How does one preserve truth? We ask Master Gotama about the preservation of truth.”
“If a person has faith, Bhāradvāja, he preserves truth when he says: ‘My faith is thus’; but he does not yet come to the definite conclusion: ‘Only this is true, anything else is wrong.’ In this way, Bhāradvāja, there is the preservation of truth; in this way he preserves truth; in this way we describe the preservation of truth. But as yet there is no discovery of truth.
“If a person approves of something…if he receives an oral tradition…if he reaches a conclusion based on reasoned cogitation…if he gains a reflective acceptance of a view, he preserves truth when he says: ‘My reflective acceptance of a view is thus’; but he does not yet come to the definite conclusion: ‘Only this is true, anything else is wrong.’ In this way too, Bhāradvāja, there is the preservation of truth; in this way he preserves truth; in this way we describe the preservation of truth. But as yet there is no discovery of truth.”
-MN 95 (excerpt)
“There are, sir, some ascetics and brahmins who come to Kesamutta. They explain and promote only their own doctrine, while they attack, badmouth, disparage, and smear the doctrines of others. Then some other ascetics and brahmins come to Kesamutta. They too explain and promote only their own doctrine, while they attack, badmouth, disparage, and smear the doctrines of others. So, sir, we’re doubting and uncertain: ‘I wonder who of these respected ascetics and brahmins speaks the truth, and who speaks falsehood?’”
“It is enough, Kālāmas, for you to be doubting and uncertain. Doubt has come up in you about an uncertain matter.
Please, Kālāmas, don’t go by oral transmission, don’t go by lineage, don’t go by testament, don’t go by canonical authority, don’t rely on logic, don’t rely on inference, don’t go by reasoned train of thought, don’t go by the acceptance of a view after deliberation, don’t go by the appearance of competence, and don’t think ‘The ascetic is our respected teacher.’ But when you know for yourselves: ‘These things are unskillful, blameworthy, criticized by sensible people, and when you undertake them, they lead to harm and suffering’, then you should give them up.
What do you think, Kālāmas? Does greed come up in a person for their welfare or harm?”
“Harm, sir.”
“A greedy individual, overcome by greed, kills living creatures, steals, commits adultery, lies, and encourages others to do the same. Is that for their lasting harm and suffering?”
“Yes, sir.”
“What do you think, Kālāmas? Does hate come up in a person for their welfare or harm?”
“Harm, sir.”
“A hateful individual, overcome by hate, kills living creatures, steals, commits adultery, lies, and encourages others to do the same. Is that for their lasting harm and suffering?”
“Yes, sir.”
“What do you think, Kālāmas? Does delusion come up in a person for their welfare or harm?”
“Harm, sir.”
“A deluded individual, overcome by delusion, kills living creatures, steals, commits adultery, lies, and encourages others to do the same. Is that for their lasting harm and suffering?”
“Yes, sir.”
“What do you think, Kālāmas, are these things skillful or unskillful?”
“Unskillful, sir.”
“Blameworthy or blameless?”
“Blameworthy, sir.”
“Criticized or praised by sensible people?”
“Criticized by sensible people, sir.”
“When you undertake them, do they lead to harm and suffering, or not? Or how do you see this?”
“When you undertake them, they lead to harm and suffering. That’s how we see it.”
“So, Kālāmas, when I said: ‘Please, don’t go by oral transmission, don’t go by lineage, don’t go by testament, don’t go by canonical authority, don’t rely on logic, don’t rely on inference, don’t go by reasoned train of thought, don’t go by the acceptance of a view after deliberation, don’t go by the appearance of competence, and don’t think “The ascetic is our respected teacher.” But when you know for yourselves: “These things are unskillful, blameworthy, criticized by sensible people, and when you undertake them, they lead to harm and suffering”, then you should give them up.’ That’s what I said, and this is why I said it.
-AN 3.65 (excerpt)
There is also a sutta (or suttas) that talks about going to see one’s wise friends and companions when confused about the teachings and asking them to help clear up one’s doubts. I don’t remember the reference, so perhaps someone can post it.
There’s also the fourth precept. Say you know when you know and you don’t know when you don’t know. Don’t say you know when you don’t know and you don’t know when you know. I think this can be applied internally as well. Being really truthful about your thoughts and tendencies is hard. It’s certainly a work in progress for me.
Ajahn Jayasaro’s Yellow Page Teaching (Vol 1, page 66) really resonates with me. I often uncover things I did not want to admit were present in my mind. Developing humility is really important.
What he is not saying is that there are levels and levels of ignorance!