|Occam is usually credited with the statement, 'Entities are not to be multiplied beyond necessity...', but it and similar statements are attributed to various people, including Galileo.
Occam also put it another way, 'It is vain to do with more what can be done with fewer.'
Another way to state it, more directly applicable to what we are talking about, is that when more than one explanation of an observation is available, we should provisionally choose the one that involves the minimum number of assumptions.
Put in more contemporary everyday terms it's the KISS principle; keep it simple stupid.
William of Occam was born in Ockham in Surrey and some spell his name Ockham as in the name of the town although others say he was from Ockham in Yorkshire. It's fairly certain that he was born in the last decade of the thirteenth century and that he died on the tenth of April.
It's not clear whether he died in thirteen forty-nine or thirteen fifty, but it was more probably thirteen forty-nine because the Black Death was at its height then. He was an Oxford scholar and studied in Paris before he challenged Pope John the twenty-second over poverty.
To find out more about Occam and his 'razor' click here to go to links.