Using this distinction between the two truths, the key insight of the ‘middle path’ may be expressed as follows. The ultimate truth about sentient beings is just that there is a causal series of impermanent, impersonal psychophysical elements. Since these are all impermanent, and lack other properties that would be required of an essence of the person, none of them is a self. But given the right arrangement of such entities in a causal series, it is useful to think of them as making up one thing