It will be entirely a work of explanation; there will be no predictions, no tests of its correctness

From Impossibility: The Limits of Science and the Science of Limits by John D. Barrow, page 3.

Complete knowledge is a tempting pie in the sky. Although it appears in some commentator's minds as the obvious goal of science, it is a concept largely unknown within the writings of contemporary science. It is the hallmark of many varieties of pseudo-science, just as it pervades countless ancient myths and legends about the origin and nature of the world. These stories leave nothing out: they have an answer for everything. They aim to banish the insecurity of ignorance and provide a complete interlinked picture of the world in which human beings play a meaningful role. They remove the worrying idea of the unknown. If you are at the mercy of the wind and the rain it helps to personify those unpredictable elements as the character traits of a storm god. Even today, many spurious attempts to explain the world around us still bear this hallmark. Horoscopes seek to create a spurious determinism that links our personalities to the orientations of the stars. Uncertainties about tomorrow can be hidden behind vague generalities about the future course of events. It is strange how many inhabitants of modern democracies feel no qualms about living under an astral dictatorship that would plan their every thought and action.

This desire for complete seamless explanation infests most examples of crank science. When somebody mails me their explanation of the architecture of the Universe derived from the geometry of the Great Pyramid, or the cipher of the Kabbalah, it will usually display a number of features: it will be entirely a work of explanation; there will be no predictions, no tests of its correctness; and nothing lies beyond its encompass. It is not the beginning of any research programme. Beyond refutation, it is always the last word.