In philosophy, metaphysical necessity, sometimes called broad logical necessity, is one of many different kinds of necessity, which sits between logical necessity and nomological (or physical) necessity, in the sense that logical necessity entails metaphysical necessity, but not vice versa, and metaphysical necessity entails physical necessity, but not vice versa. A proposition is said to be necessary if it could not have failed to be the case. Nomological necessity is necessity according to the laws of physics and logical necessity is necessity according to the laws of logic, while metaphysical necessities are necessary in the sense that the world could not possibly have been otherwise. What facts are metaphysically necessary, and on what basis we might view certain facts as metaphysically but not logically necessary are subjects of substantial discussion in contemporary philosophy. The concept of a metaphysically necessary being plays an important role in certain arguments for the existence of God, especially the ontological argument, but metaphysical necessity is also one of the central concepts in late 20th century analytic philosophy. Metaphysical necessity has proved a controversial concept, and criticized by David Hume, Immanuel Kant, J. L. Mackie, and Richard Swinburne, among others. Types of necessity Metaphysical necessity is contrasted with other types of necessity. For example, the philosophers of religion John Hick and William L. Rowe distinguished the following three: factual necessity (existential necessity): a factually necessary being is not causally dependent on any other being, while any other being is causally dependent on it. causal necessity (subsumed by Hick under the former type): a causally necessary being is such that it is logically impossible for it to be causally dependent on any other being, and it is logically impossible for any other being to be causally independent of it. logical necessity: a logically necessary being is a being whose non-existence is a logical impossibility, and which therefore exists either timeless or eternally in all possible worlds. Hume's dictum Hume's dictum is a thesis about necessary connections between distinct entities. Its original formulation can be found in David Hume's A Treatise of Human Nature: "There is no object, which implies the existence of any other if we consider these objects in themselves". Hume's intuition motivating this thesis is that while experience presents us with certain ideas of various objects, it might as well have presented us with very different ideas. So when I perceive a bird on a