William of Occam may have been the first practitioner of the K.I.S.S. principle.
"Occam's Razor" is the best known principle of 14th Century logician William of Occam (or, if you prefer, Ockam).
"Pluralitas non est podenda sine necessitate."
"Frusta fit per plura quod potest fieri per pauciora."
"Entita non sunt multiplicanda praeter necessitandem."
Apparently, the first two are attributable to Occam, the other may have been extrapolated later by Liebnitz and others. William of Occam used his razor to piss off the Pope, saying things like "God's existence cannot be deduced by reason alone."
The main principle states that "entities should not be multiplied unnecessarily".
Later adaptations include "we are not to admit no more causes to natural things than such as are both true and sufficient to explain their appearances".
Scientists use Occam's razor thus: "When you have two competing theories which make exactly the same predictions, the one that is simpler is the better."
No lesser mortal than Steven Hawking invokes Occam's razor in A Brief History of Time: "We could still imagine that there is a set of laws that determines events completely from some supernatural being, who could observe the present state of the universe without disturbing it. However, such models of the universe are not of much interest to us mortals. It seems better to employ the principle known as Occam's razor and cut out all the features of the theory that cannot be observed."
[Illustration by Kristen Abkemeier]