Noodwendigheid (of noodsaaklikheid) verwys na die eienskap van iets wat nie anders kan as om te bestaan nie. ‘n Noodwendige wese is een wie se bestaan nie afhanklik is van enigiets anders nie, en wat in alle moontlike werklikhede sou bestaan het. Wiskundige waarhede soos 2 + 2 = 4 kan as noodwendig beskou word – hulle is altyd waar. Maar belangriker: God se bestaan word in klassieke teisme as noodwendig beskou, omdat Hy nie kan nie bestaan nie. Hy bestaan uit Homself, onvermydelik en altyd. Hierdie idee is sentraal in die klassieke siening van God as die grond van alle ander dinge se bestaan.
Necessity refers to the property of something that cannot but exist. A necessary being is one whose existence does not depend on anything else and that would have existed in all possible realities. Mathematical truths such as 2 + 2 = 4 can be regarded as necessary – they are always true. But more importantly: God’s existence is regarded in classical theism as necessary, because He cannot not exist. He exists from Himself, inevitably and always. This idea is central to the classical view of God as the ground of the existence of all other things.