The postings on this blog have often referred to Ockham's Razor, the philosophical principle that can be variously stated as "Do not needlessly multiply hypotheses," or "Do not use a more complicated explanation when a simpler explanation will suffice," or "When two hypotheses account for the same facts, prefer the simpler." The Razor is a fundamental principle of science, although certainly not the only reason for our confidence in scientific knowledge.
There is of course no "proof" of the Razor. It is grounded in intuition, perhaps esthetics. Whatever proof it has is in the pudding; science has been fabulously successful at providing practical, reproducible, consensus knowledge of the world.
William of Ockham, a 14th-century English Franciscan scholar gets the credit, but he hardly invented the Razor. It has precedents going back at least to Aristotle, although the Razor was always at odds with supernaturalists, including the institutional Church and Divine-Right governments, who stood (and still stand) only to gain by a multiplication of powers that require for their management a priestly or privileged caste. Indeed, we know of William of Ockham primarily because of his tussles with the Pope.
Newton built the Razor into the philosophical foundations of physics. "We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearance," he insists at the very beginning of the Principia. His theory of universal gravitation -- a single elegantly simple formula describes the motions of planets, moons, tides, and the fall of the apple -- is the Razor at its best. William Rowan Hamilton's Principle of Least Action fashioned the Razor into a mathematical axiom of mechanics.
Most of us -- myself included -- live in a mire of the superfluous, ideas and concepts that comfort and compose: traditional religion, for example, what the poet Philip Larkin called "that vast, moth-eaten musical brocade," or all the other pseudo-religions -- astrology, parapsychology, xenophobia, etc. -- that we use to fill the hours, but which merely distract us from the crystalline simplicity of life pared to the bone. How I long for the clean purity of a sunrise over the water meadow, the razor slant of light, the memory, in that sufficient radiance, of a touch, an hour earlier, in the darkness of the bedroom, a brief and precious talisman of love.