About Mass (1)

There is an obvious problem here:

To verify the first postulate, we assumed that the mass in F=ma is the same in all reference frames, which contradicts the conclusion of Special Relativity. How can we disapprove Special Relativity using the Newtonian view?

Where does the first postulate come from? It comes from induction.

Here is the general process of induction:
We see one pig is black, another pig is also black, all pigs we have ever seen are all black, so we conclude that all pigs are black. If one day we find a white pig, then our conclusion will be invalidated.

The first postulate has to start from somewhere. Through the example of the falling apple, we know Newton's second law of motion is one supporting evidence of the first postulate. If you can find any contradicting example, the first postulate will be gone.