it is more generally a part of human cognition. To distinguish properties of languages that can be traced to other facts regarding cognition from properties of languages that cannot, the abbreviation UG* can be used. UG is the term often used by Chomsky for those aspects of the human brain which cause language to be the way that it is (i.e. are universal grammar in the sense used here), but here for the purposes of discussion, it is used for those aspects which are furthermore specific to language (thus UG, as Chomsky uses it, is just an abbreviation for universal grammar, but UG* as used here is a subset of universal grammar). In the same article, Chomsky casts the theme of a larger research program in terms of the following question: "How little can be attributed to UG while still accounting for the variety of 'I-languages' attained, relying on third factor principles?" (I-languages meaning internal languages, the brain states that correspond to knowing how to speak and understand a particular language, and third factor principles meaning "principles not specific to the Faculty of Language" in the previous quote). Chomsky has speculated that UG might be extremely simple and abstract, for example only a mechanism for combining symbols in a particular way, which he calls "merge". The following quote shows that Chomsky does not use the term "UG" in the narrow sense UG* suggested above: "The conclusion that merge falls within UG holds whether such recursive generation is unique to FL (faculty of language) or is appropriated from other systems." In other words, merge is seen as part of UG because it causes language to be the way it is, universal, and is not part of the environment or general properties independent of genetics and environment. Merge is part of universal grammar whether it is specific to language, or whether, as Chomsky suggests, it is also used for example in mathematical thinking. The distinction is the result of the long history of argument about UG*: whereas some people working on language agree that there is universal grammar, many people assume that Chomsky means UG* when he writes UG (and in some cases he might actually mean UG* [though not in the passage quoted above]). Some students of universal grammar study a variety of grammars to extract generalizations called linguistic universals, often in the form of "If X holds true, then Y