In philosophy, universality is the idea that universal facts exist and can be progressively discovered, as opposed to relativism. In certain theologies, universalism is the quality ascribed to an entity whose existence is consistent throughout the universe, whose being is independent of and unconstrained by the events and conditions that compose the universe, such as entropy and physical locality.
When used in the context of ethics, the meaning of universal refers to that which is true for "all similarly situated individuals."Rights, for example in natural rights, or in the 1789 Declaration of the Rights of Man and of the Citizen, for those heavily influenced by the philosophy of the Enlightenment and its conception of a human nature, could be considered universal. The 1948 Universal Declaration of Human Rights is inspired by such principles.
In logic, or the consideration of valid arguments, a proposition is said to have universality if it can be conceived as being true in all possible contexts without creating a contradiction. Some philosophers have referred to such propositions as universalizable. A truth is considered to be universal if it is logically valid (logical) in and also beyond all times and places. Hence a universal truth is considered logically to transcend the state of the physical universe, whose order is derived from such truths. In this case, such a truth is seen as eternal or as absolute. The patterns and relations expressed by mathematics in ways that are consistent with the fields of logic and mathematics are typically considered truths of universal scope. This is not to say that universality is limited to mathematics, since it is also used in philosophy, theology, and other pursuits.
The relativist conception denies the existence of some or all universal truths, particularly ethical ones (as moral relativism). Though usage of the word truth has various domains of application, relativism does not necessarily apply to all of them.
In metaphysics, a universal is a type, a property, or a relation. The noun universal contrasts with individual, while the adjective universal contrasts with particular or sometimes with concrete. The latter meaning, however, may be confusing since Hegelian and neo-Hegelian (e.g. British idealist) philosophies speak of concrete universals.
A universal may have instances, known as its particulars. For example, the type dog (or doghood) is a universal, as are the property red (or redness) and the relation betweenness (or being between). Any particular dog, red thing, or object that is between other things is not a universal, however, but is an instance of a universal. That is, a universal type (doghood), property (redness), or relation (betweenness) inheres a particular object (a specific dog, red thing, or object between other things).
Platonic realism holds universals to be the referents of general terms, i.e. the abstract, nonphysical entities to which words like "doghood", "redness", and "betweenness" refer. By contrast, particulars are the referents of proper names, like "Fido", or of definite descriptions that identify single objects, like the phrase, "that apple on the table". By contrast, other metaphysical theories merely use the terminology of universals to describe physical entities.
The problem of universals is an ancient problem in metaphysics concerning the nature of universals, or whether they exist. Part of the problem involves the implications of language use and the complexity of relating language to ontological theory.
Universal truth is regarded as ontic, i.e. expressing the order of being itself. A universal truth is epistemic only to the extent that its ontic expression is apprehended or discerned in a veridical way, which cannot affect its being in any case. Most ontological frameworks do not consider classes to be universals, although some prominent philosophers, such as John Bigelow, do.