Universality is the quality ascribed to in existence throughout the universe. In philosophy, universalism is a doctrine or school in which it is claimed that universal facts can be discovered and which is understood then as being in opposition to relativism. 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 as 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. Truth is considered to be universal if it is valid in all times and places. In this case, it is seen as eternal or as absolute. The relativist conception denies the existence of some or all universal truths, particularl ethical ones (through moral relativism). Mathematics is a field in which those truths discovered, in relation to the field of mathematics, are typically considerered of universal scope. Usage of the word truth has various domains of application, relativism does not necessarily apply to all of them.
A universal proposition is one that affirms a property of all the members of a set. For instance, the proposition that all dogs are mortal and the proposition that all cows can fly are universal propositions, the former (assumedly) true and the latter false. A universal proposition is logically equivalent to the negation of an existential proposition. Thus, claiming that all cows can fly is equivalent to denying that there is a cow that cannot fly.
It may be noted, along the lines of Humean causal scepticism, that the only universal propositions that must be true are those that exist a priori, drawn from definitions (i.e. "All dogs are mammals"). Universal propositions that are drawn a posteriori, from one's experience of the world (i.e. "All dogs are born with four legs"), can never be confirmed as certainly true, simply supported as likely to be true give the evidence available, making such propositions falsifiable.
Universality in metaphysics
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.
Most ontological frameworks do not consider classes to be universals, although some prominent philosophers, such as John Bigelow, do.
The term universality also refers to the medieval concept of an absolute, all-encompassing morality that justified a universal secular rule by one all-powerful Holy Roman Emperor, and also justified as universal the religious rule by one all-powerful all-encompassing (hence the term catholic) church. In the 17th century, the doctrine of universality gave way to the doctrine of raison d'état or national interest. Universality is comparable, but not equivalent, to the concept of the Mandate of Heaven in Chinese history.
As a state (truth)
Absolutism contends that in a particular domain of thought, all statements in that domain are either absolutely true or absolutely false: none is true for some cultures or eras or individuals while false for others. These statements are called absolute truths.
One could ask, 'Is it true that truth exists?' One can also ask, 'Is it true that truth does not exist?' The first can be affirmed by mind, while the latter cannot be affirmed without a gross distortion of sense. If truth does not exist, it would certainly be true that truth does not exist. That is the quality of absolute truth. If the negation were true, one could not ask the question and expect a true answer.
As an action (verity)
In action form, absolute truth most closely represents verity. This form can be likened to the action usage of metaphysical truth, but not its state usage (which represent metaphysical truths in state form). Absolute truth in action form is considered by many to be metaphysical only, and therefore the same as the action usage of metaphysical truth. Some believe the outcome of absolute truth (verity) can be metaphysical truths, physical truths or both, but by definition not any form of a lie.
"What is absolutely true is always correct, everywhere, all the time, under any condition. An entity's ability to discern these things is irrelevant to that state of truth." - Steven Robiner
- Kant's categorical imperative: "Act only according to that maxim by which you can at the same time will that it would become a universal law."
- 1948 Universal Declaration of Human Rights