David Deutsch

Everett interpretation of quantum theory

speaking about certain sensations that palaeontologists have when they gaze at fossils. The sensations are real, but the dinosaurs were not. Or, if they were, we can never know of them. The latter is one of many tangles that one gets into via the justified-true-belief theory of knowledge – for in reality here we are, knowing of them. Then there is the ‘interpretation’ that the fossils themselves come into existence only when they are extracted from the rock in a manner chosen by the palaeontologist and experienced in a way that can be communicated to other palaeontologists. In that case, fossils are certainly no older than the human species. And they are evidence not of dinosaurs, but only of those acts of observation. Or one can say that dinosaurs are real, but not as animals, only as a set of relationships between different people’s experiences of fossils. One can then infer that there is no sharp distinction between dinosaurs and palaeontologists, and that ‘classical language’, though unavoidable, cannot express the ineffable relationship between them. None of those ‘interpretations’ is empirically distinguishable from the rational explanation of fossils. But they are ruled out for being bad explanations: all of them are general-purpose means of denying anything. One can even use them to deny that Schrödinger’s equation is true.

Since explanationless prediction is actually impossible, the methodology of excluding explanation from a science is just a way of holding one’s explanations immune from criticism. Let me give an example from a distant field: psychology.