Ockham's Razor
It is "sometimes inaccurately paraphrased as "the simplest explanation is usually the best one." The idea is frequently attributed to English Franciscan friar William of Ockham (c. 1287–1347), a scholastic philosopher and theologian, although he never used these words. This philosophical razor advocates that when presented with competing about the same prediction, one should select the solution with the fewest assumptions, and that this is not meant to be a way of choosing between hypotheses that make different predictions."" (Wikipedia)