The claim of the freedom of the will (understood as an individual who is transcendent to Nature) in the name of XXth century scientific knowledge, against the perspective of XVIIIth-XIXth century scientific materialism, is analysed and refuted in the present paper. The hypothesis of reductionism finds no obstacle within contemporary natural sciences. Determinism in classical physics is irrefutable, unless classical physics is itself refuted. From quantum mechanics, some authors argue that free will is possible because there is an ontological indeterminism (...) in the natural laws, and that the mind is responsible for the wave function collapse of matter, which leads to a choice among the different possibilities for the body. However, here I defend the opposite thesis because indeterminism does not imply free will, and because the considerations about an autonomous mind sending orders to the body is against neuroscience or evolutionary theories about human beings. The quantum theory of measurement can be interpreted without the intervention of human minds, but other fields of science cannot contemplate the mentalist scenario. A fatalistic or materialist view, which denies the possibility of a free will, makes much more sense in scientific terms. (shrink)