You can think all kinds of things. But you can't know for sure.

You don't know that for certain

And I don't know what I feel or what I want to feel. I don't know what to think or what I am.

I don't know what I feel or what I want to feel. I don't know what to think or what I am.

What if we shifted our definition of "I don't know" from the negative frame ("I have no idea" or "I know nothing about that," which feels like we lack competence or confidence) to a more neutral frame? What if we thought about it as recognizing that, although we might know something about the chances of some event occurring, we are still not sure how things will turn out in any given instance? That is just the truth. If we accept that, "I'm not sure" might not feel so bad. What good poker players and good decision-makers have in common is their comfort with the world being an uncertain and unpredictable place.

I doubt, therefore I think, therefore I am.

"What makes you so certain?"
"But I am not certain," I told him. "Nothing is certain. You want certainty?"
"Yes!"
"Then you want death."

if you think you know what is going on, you haven’t got a clue about what’s going on.

Dubito ergo cogito, cogito ergo sum'
(I doubt therefore I think, I think therefore I am)

There are some things that you know to be true, and others that you know to be false; yet, despite this extensive knowledge that you have, there remain many things whose truth or falsity is not known to you. We say that you are uncertain about them. You are uncertain, to varying degrees, about everything in the future; much of the past is hidden from you; and there is a lot of the present about which you do not have full information. Uncertainty is everywhere and you cannot escape from it.

Excuse me, I am not convinced.

What I do not know, I do not think I know.

I think, therefore I doubt.

They're all crazy. They're all crazy except you and me. Sometimes I have me doubts about you.