Consider the example of a simple harmonic oscillator initially at rest with amplitude A. Suppose that this system was placed inside a light-tight container such that one could only view it using a camera which can only take a snapshot of what's happening inside. Each snapshot has some probability of seeing the oscillator at any possible position x along its trajectory. The classical probability density encapsulates which positions are more likely, which are less likely, the average position of the system, and so on. To derive this function, consider the fact that the positions where the oscillator is most likely to be found are those positions at which the oscillator spends most of its time. Indeed, the probability of being at a given x -value is proportional to the time spent in the vicinity of that x -value. If the oscillator spends an infinitesimal amount of time dt in the vicinity dx of a given x -value, then the probability P (x) dx of being in that vicinity will be