The fact of believing is based on the intrinsic principle that all knowledge that is not verified is a belief.
There is no physical law that is undeterministic. From the wave function equations to other quantum mechanical equations, physics is deterministic, at a mathematical level. The conflict arises when the human being wants to understand the wave function. The human being perceives the world through particles, he cannot perceive the world as a wave function, hence why quantum mechanics is counter-intuitive and many people ignorant of physics tell you that quantum mechanics makes the world "probabilistic" and therefore, undetermined, which is false. There is no freedom of choice in the quantum world.
At the macroscopic level, physics remains deterministic. Time, although relative, advances in one direction and the four elemental forces establish determinism. The fact that you appeal to the law, and that on the other hand, you appeal to free will is a contradiction that you seek to resolve through a fallacious argument: that physical reality is not governed by mathematical and predictive principles. Thus, you will not find even in what we call "consciousness" a loophole of freedom of choice in the human mind if we attend to the fundamental principle that the human being is also governed by physical laws.