Physics is an exact natural science, yet uncertainty plays a growing role. By dissociating Aristotle’s efficient and final causes, Galileo and classical physics reduced everything to what could be calculated, so that uncertainty was destined to disappear in principle. The advent of quantum physics, with its principle of indeterminacy, led to a radical uncertainty that has been shown not to be caused by “hidden variables”. This invites us henceforth to distinguish between Being (in itself) and Existence, that is, perceived phenomena, all of which proceed from Being, although Being cannot be reduced to them. This strangeness of Being and its capacity to say “No” to us paradoxically guarantee that physical laws are not the sole product of our (inter)subjectivity. Thus, the sceptical attitude and its symmetrical counterpart – absolute domination through knowledge – become unreasonable. An analogy is suggested with the principles of psychoanalytical practice.