Uncertainty may result from (1) an impossibility to measure what we want to measure, or an impossibility to observe the system, (2) the limited precision of our measurement, (3) the measurement fundamentally disturbing the system and, as such, causing the information to be unreliable, (4) an uncertainty that is inherent to Nature (Copenhagen interpretation). We agree with Lorentz’s and Einstein’s viewpoint: there is no need to elevate indeterminism to a philosophical principle. The more important question is: how does quantum physics model it? How does it deal with it? This paper wants to offer some thoughts on that, supporting Lorentz’s (and Einstein’s) position: we only have statistical indeterminism. Quantum physics should, therefore, not be seen as a radical departure from classical physics. Quantum-mechanical uncertainty is nothing but statistical indeterminism. This is, effectively, the fifth interpretation of uncertainty which should be added to the list above, and may well be the final one. The position is illustrated with a detailed discussion of the wavefunction(s) in the context of Schrödinger’s wave equation for the hydrogen atom. We also further explore the question in regard to the (possible) physical dimension of the real and imaginary part of the wavefunction. To paraphrase Feynman, we wonder what could be ‘sloshing back and forth’ between the real and imaginary part of the wavefunction? We think it is kinetic and potential energy. We, therefore, briefly present our two-dimensional oscillator model again, but using the metaphor of a multi-piston radial engine as a metaphor this time.