The structure of understanding — cause, action/motion, effect — reflects that of time — past, present, future — and, like time, is wholly contained in the moment. Understanding exists in the moment as a set of expectations, which might be described as probabilities. Such a set is coherent when each expectation lies between 0 and 1 and, across a set of mutually exclusive and exhaustive outcomes, the expectations sum to 1. For example, I might expect a delivery before noon with P(before noon) = 0.3, between noon and one with P(noon–one) = 0.1, and after one with P(after one) = 0.6. This is a coherent understanding: ΣP = 1. Were my expectations instead 0.5, 0.5 and 0.5 across the same three intervals, ΣP = 1.5, and the understanding would be incoherent. And an understanding coherent in one moment may be incoherent in another. Held at half past one, with nothing delivered, the first set fails: noon has passed, so P(before noon) can no longer be 0.3 — it must be 0.

Like music, understanding fuses past and future with the present moment.