A linguistic universal is a pattern that occurs systematically across natural languages, potentially true for all of them. For example, All languages have nouns and verbs, or If a language is spoken, it has consonants and vowels. Research in this area of linguistics is closely tied to the study of linguistic typology, and intends to reveal generalizations across languages, likely tied to cognition, perception, or other abilities of the mind. The field originates from discussions influenced by Noam Chomsky's proposal of a Universal Grammar, but was largely pioneered by the linguist Joseph Greenberg, who derived a set of forty-five basic universals, mostly dealing with syntax, from a study of some thirty languages. Though there has been significant research into linguistic universals, in more recent time some linguists, including Nicolas Evans and Stephen C. Levinson, have argued against the existence of absolute linguistic universals that are shared across all languages. These linguists cite problems such as ethnocentrism amongst cognitive scientists, and thus linguists, as well as insufficient research into all of the world's languages in discussions related to linguistic universals, instead promoting these similarities as simply strong tendencies. Terminology Linguists distinguish between two kinds of universals: (opposite: , often called ) and (opposite: ). Absolute universals apply to every known language and are quite few in number; an example is All languages have pronouns. An implicational universal applies to languages with a particular feature that is always accompanied by another feature, such as If a language has trial grammatical number, it also has dual grammatical number, while non-implicational universals just state the existence (or non-existence) of one particular feature. Also in contrast to absolute universals are , statements that may not be true for all languages but nevertheless are far too common to be the result of chance. They also have implicational and non-implicational forms. An example of the latter would be The vast majority of languages have nasal consonants. However, most tendencies, like their universal counterparts, are implicational. For example, With overwhelmingly greater-than-chance frequency, languages with normal SOV order are postpositional. Strictly speaking, a tendency is not a kind of universal, but exceptions to most statements called universals can be found. For example, Latin is an SOV language with prepositions. Often it turns out that these exceptional languages are undergoing a shift from one type of language to another. In the case of Latin, its descendant Romance languages switched to