How we determine facts.

[Heywood]

Unfortunately, at no point does proof that all the marbles are white materialize until all marbles are out. However, I agree that we do use sloppy thinking like that all the time. It isn't a "fact of reality" that you're discovering, you're engaging in a useful heuristic (congratulations, you're describing what we already knew about the limitations of our minds and assumptions).

-because our brains didn't evolve to seek truth.

In the example in the OP there are two propositions:
Proposition A) All the marbles are white.
Proposition B) Not all the marbles are white.

Only one proposition can be true. Each time you draw a marble and find it to be white, while never drawing a marble and finding it to be black.....each time you do that the probability that proposition A is true becomes more likely.

Is the speed of light in a vacuum really a constant? We don't know for absolute certainty. We consider it to be a fact because we have made many many observations and each one adds to our confidence in the veracity of proposition that the speed of light in a vacuum is constant.

---

Only if you know how many marbles are in the bag, of course. If you don't know that, then you have no means of determining the probability at all, and are just talking out your ass if you begin to assign probabilities to the colors of the marbles based on what you've already drawn.

The example I used in the OP works for any bag of marbles containing N number of marbles. The probability that all the marbles are white always moves closer to 1 with each draw of a white marble while never drawing a black one. You can work this out for yourself with 4 marbles or 5...or 10,000 marbles.

Suppose you have 3 colors of marbles. White, red, and blue. You can consider red and blue to be non-white marbles(or black). It really doesn't matter how many different colors the bag could contain. The bag either contains all white marbles or it does not.