If you wish to pretend to be deliberately dense, you certainly may.
Free country.
The theories and laws of science cannot be proved, only confirmed or falsified.
However, assuming the theory or law to be true, deductions can be made (proven), and then tested.
Given Newton's theory of gravity, we can calculate the trajectory something will follow. Any introductory text on the subject, or many calculus texts, will have the proof that there is an escape velocity. But keep in mind that the proof assumes the truth of the *unproven* theory.