If \(\EC_b\) and \(\EC_c\) cannot be combined, which is the correct framework to use in describing a harmonic oscillator? The answer, again a key point in the histories interpretation, which will be discussed in more detail in section 5, and also section 11, is that in the quantum world there is never a single correct framework, there are always many possibilities, something rather strange from the perspective of classical physics. The single framework rule prohibits combining incompatible frameworks; it does not assert that there is just one correct framework to use in modeling a particular physical situation.