Is there any proof of assertion that "assertion can be proved"?

Question

Here's some reason to doubt any proof:

• Dissent – The uncertainty demonstrated by the differences of opinions among philosophers and people in general.
• Progress ad infinitum – All proof rests on matters themselves in need of proof, and so on to infinity.
• Relation – All things are changed as their relations become changed, or, as they are looked upon from different points of view.
• Assumption – The truth asserted is based on an unsupported assumption.
• Circularity – the truth asserted involves a circularity of proofs

Source: https://en.m.wikipedia.org/wiki/Agrippa_the_Skeptic

https://en.m.wikipedia.org/wiki/M%C3%BCnchhausen_trilemma

We can doubts anything even someone doubt existence of self, God, mind, external reality, time, consistency, etc.

But why in first place we think that even something can be proved without proof?

So question is is there any proof of assertion that "assertion can be proved"?

To express more clearly:

Assertion: a confident and forceful statement of fact or belief.

Proof: the action of establishing the truth of a statement.

Action: the fact or process of doing something, typically to achieve an aim.

And it is in metaphysical sense.

Answer 1

It’s certainly true that much less is “proven” than we intuitively like to think. We can still formulate local concepts in maths like “proof in classical axiomatic set theory ZFC”. These embrace the “Assumptions” objection by wearing the Axioms of a given proof clearly on their sleeves - yes, this proof relies on some assumptions, but they are assumptions that are clearly stated and that you don’t have to believe uncritically to be true in order to appreciate that some construction is, indeed, a valid proof in that system.

Answer 2

In On Certainty Wittgenstein explains how systematic doubt is impractical. Even solipsists who claim every one around them is just a product of their imagination continue to interact with them as if they were real. If they did not, they would soon run put of food, clothes, a place to live...

Similarly, one can affect to doubt that logic is even real and pretend that nothing can be proved. They can say they doubt the Pythagorean theorem and its demonstration and consequences. But still, remains the fact that each time they will draw a rectangle of sides 3, 4 and 5, the angle between 3 and 4 will always be 90 degrees. And that at the end of the day, they prefer to live in soundly built houses, with parallel walls and a straight ceiling.

Some demonstrations just work. If I can observe a fact A (my wheel is of diameter 1) and a fact B (each turn of the wheel my chariot advances by more or less 3.14) , have a demonstration that a circle circumference is diameter times Pi, and all the while each time I try to measure any wheel I find the same result, it is only practical to admit that something is valid here.