Abstract
When pair-Merge takes two phrases and forms an ordered pair, AdjP (adjunct phrase) becomes invisible since such AdjP has been pair-merged on a separate plane (see Chomsky (2004)). When pair-Merge takes two heads, say v*, √root, and forms <√root, v*>, v* becomes invisible since v* is affixal (see Chomsky (2015a: 12)). There is, however, no purely conceptual ground for supporting the analysis of the adjunction on a separate plane or the invisibility of affixes. Thus, both of these assumptions are conceptually dubious. To solve this problem, I reformulate pair-Merge of heads by adopting a definition of an ordered pair in set theory. Finally, it is shown that the reformulation explains empirical facts such as the double object construction, the cognate object construction, the small clause construction and the ECM (Exceptional Case Marking) construction.
