Anselm of Canterbury (1033 -- 1109) was a medieval theologian  According to Anselm' s ontological argument for the existence of God, accidental beings are all those things -- essentially all sense objects -- whose non-existence could be imagined without inherent contradiction, and necessary beings are those things whose existence is guaranteed precisely by what they are
Because accidental beings could not have guaranteed that they ever would come into existence, there must be a necessary being upon whom all the accidental beings depends to bring them into existence; and this necessary being Anselm identifies with God, who ttherefore clearly must exist
It presents as evidence in support of a claim information that is inconsistent with other evidence presented in support of the same claim.