Occam's razor - A simple and practical idea!

 

Occam's razor

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"Ockham's razor" redirects here. For the aerial theatre company, see Ockham's Razor Theatre Company. For the Australian radio program, see Radio National.

Manuscript illustration of William of Ockham

Occam's razor, Ockham's razor, Ocham's razor (Latin: novacula Occami), or the principle of parsimony or law of parsimony (Latin: lex parsimoniae) is the problem-solving principle that "entities should not be multiplied beyond necessity",^[1][2] sometimes inaccurately paraphrased as "the simplest explanation is usually the best one."^[3] The idea is attributed to English Franciscan friar William of Ockham (c.  1287–1347), a scholastic philosopher and theologian who used a preference for simplicity to defend the idea of divine miracles. This philosophical razor advocates that when presented with competing hypotheses about the same prediction, one should select the solution with the fewest assumptions,^[4] and that this 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.^[5][6] 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 failing explanations can always be burdened with ad hoc hypotheses to prevent them from being falsified, simpler theories are preferable to more complex ones because they tend to be more testable.^[7][8][9]

St. Thomas Aquinas, in the Summa Theologica, uses a formulation of Occam's razor to construct an objection to the idea that God exists, which he refutes directly with a counterargument:^[63]

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.

In turn, Aquinas answers this with the quinque viae, and addresses the particular objection above with the following answer:

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.