Occam's razor

Occam's razor (also Ockham's razor or Ocham's razor (Latin: novacula Occami) is the problem-solving principle that states 'Entities should not be multiplied without necessity.' The idea is attributed to English Franciscan friar William of Ockham (c. 1287–1347), a scholastic philosopher and theologian. It is sometimes misquoted in pop culture and other media by some form of the statement 'The simplest solution is most likely the right one.' Occam's razor instead says that when presented with competing hypotheses that make the same predictions, one should select the solution with the fewest assumptions, and it is not meant to be a way of choosing between hypotheses that make different predictions. ... the simplest hypothesis proposed as an explanation of phenomena is more likely to be the true one than is any other available hypothesis, that its predictions are more likely to be true than those of any other available hypothesis, and that it is an ultimate a priori epistemic principle that simplicity is evidence for truth.Further, it is superfluous to suppose that what can be accounted for by a few principles has been produced by many. But it seems that everything we see in the world can be accounted for by other principles, supposing God did not exist. For all natural things can be reduced to one principle which is nature; and all voluntary things can be reduced to one principle which is human reason, or will. Therefore there is no need to suppose God's existence.Since nature works for a determinate end under the direction of a higher agent, whatever is done by nature must needs be traced back to God, as to its first cause. So also whatever is done voluntarily must also be traced back to some higher cause other than human reason or will, since these can change or fail; for all things that are changeable and capable of defect must be traced back to an immovable and self-necessary first principle, as was shown in the body of the Article. Occam's razor (also Ockham's razor or Ocham's razor (Latin: novacula Occami) is the problem-solving principle that states 'Entities should not be multiplied without necessity.' The idea is attributed to English Franciscan friar William of Ockham (c. 1287–1347), a scholastic philosopher and theologian. It is sometimes misquoted in pop culture and other media by some form of the statement 'The simplest solution is most likely the right one.' Occam's razor instead says that when presented with competing hypotheses that make the same predictions, one should select the solution with the fewest assumptions, and it is not meant to be a way of choosing between hypotheses that make different predictions. Similarly, in science, Occam's razor is used as an abductive heuristic in the development of theoretical models rather than as a rigorous arbiter between candidate models. In the scientific method, Occam's razor is not considered an irrefutable principle of logic or a scientific result; the preference for simplicity in the scientific method is based on the falsifiability criterion. For each accepted explanation of a phenomenon, there may be an extremely large, perhaps even incomprehensible, number of possible and more complex alternatives. Since one can always burden failing explanations with ad hoc hypotheses to prevent them from being falsified, simpler theories are preferable to more complex ones because they are more testable. The term Occam's razor did not appear until a few centuries after William of Ockham's death in 1347. Libert Froidmont, in his On Christian Philosophy of the Soul, takes credit for the phrase, speaking of 'novacula occami'. Ockham did not invent this principle, but the 'razor'—and its association with him—may be due to the frequency and effectiveness with which he used it. Ockham stated the principle in various ways, but the most popular version, 'Entities are not to be multiplied without necessity' (Non sunt multiplicanda entia sine necessitate) was formulated by the Irish Franciscan philosopher John Punch in his 1639 commentary on the works of Duns Scotus. The origins of what has come to be known as Occam's razor are traceable to the works of earlier philosophers such as John Duns Scotus (1265–1308), Robert Grosseteste (1175–1253), Maimonides (Moses ben-Maimon, 1138–1204), and even Aristotle (384–322 BC). Aristotle writes in his Posterior Analytics, 'We may assume the superiority ceteris paribus of the demonstration which derives from fewer postulates or hypotheses.' Ptolemy (c. AD 90 – c. AD 168) stated, 'We consider it a good principle to explain the phenomena by the simplest hypothesis possible.' Phrases such as 'It is vain to do with more what can be done with fewer' and 'A plurality is not to be posited without necessity' were commonplace in 13th-century scholastic writing. Robert Grosseteste, in Commentary on the Posterior Analytics Books (Commentarius in Posteriorum Analyticorum Libros) (c. 1217–1220), declares: 'That is better and more valuable which requires fewer, other circumstances being equal... For if one thing were demonstrated from many and another thing from fewer equally known premises, clearly that is better which is from fewer because it makes us know quickly, just as a universal demonstration is better than particular because it produces knowledge from fewer premises. Similarly in natural science, in moral science, and in metaphysics the best is that which needs no premises and the better that which needs the fewer, other circumstances being equal.' The Summa Theologica of Thomas Aquinas (1225–1274) states that 'it is superfluous to suppose that what can be accounted for by a few principles has been produced by many.' Aquinas uses this principle to construct an objection to God's existence, an objection that he in turn answers and refutes generally (cf. quinque viae), and specifically, through an argument based on causality. Hence, Aquinas acknowledges the principle that today is known as Occam's razor, but prefers causal explanations to other simple explanations (cf. also Correlation does not imply causation). William of Ockham (circa 1287–1347) was an English Franciscan friar and theologian, an influential medieval philosopher and a nominalist. His popular fame as a great logician rests chiefly on the maxim attributed to him and known as Occam's razor. The term razor refers to distinguishing between two hypotheses either by 'shaving away' unnecessary assumptions or cutting apart two similar conclusions. While it has been claimed that Occam's razor is not found in any of William's writings, one can cite statements such as Numquam ponenda est pluralitas sine necessitateWilliam of Ockham - Wikiquote ('Plurality must never be posited without necessity'), which occurs in his theological work on the Sentences of Peter Lombard (Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi; ed. Lugd., 1495, i, dist. 27, qu. 2, K). Nevertheless, the precise words sometimes attributed to William of Ockham, Entia non sunt multiplicanda praeter necessitatem (Entities must not be multiplied beyond necessity), are absent in his extant works; this particular phrasing comes from John Punch, who described the principle as a 'common axiom' (axioma vulgare) of the Scholastics. William of Ockham's contribution seems to restrict the operation of this principle in matters pertaining to miracles and God's power; so, in the Eucharist, a plurality of miracles is possible, simply because it pleases God.