As observed in section 4.2, the Extended Standard Theory of 1972 preserved the structure of theAspectsmodel,
except that certain aspects of semantic interpretation (notably quantifier scope, focus, and possibly anaphora) were
read off of Surface Structure. By 1975, the notion of a“trace of movement”(thetin sections 1.7 and 3.2) had been
introduced. This permitted all semantic interpretation to take place in terms of Surface Structure, since the Deep
Structure positions of constituents could be identified by their traces in Surface Structure.
Government-Binding Theory represents a major shift, in that two new levels of representation are introduced, both
derived fro mSurface Structure (now called S-structure) through further sequences of derivational rules (now
simplifiedtothegeneralform“Moveα”),guidedbymultipleconstraints. Oneofthesesequences, resultinginPhonetic
Form (PF), more or less duplicates the old phonological component (to the extent that anyone has ever attempted to
be explicit about it). The other sequence, which received far greater attention, results in a level called Logical Form
(LF). LF begins rather modestly (Chomsky 1975) as a way of explicitly encoding quantifier scope and anaphoric
relations in syntax, but by Chomsky (1986: 68) it is called a“direct representation of...meaning,”an“‘interface’
betweenlanguage and other cognitive systems.”Thus ittakes over thesemanticfunctionassigned tothemoreextreme
interpretationsof Deep Structure in theAspectstheory. The remnant of Deep Structure, now calledD-structure, is still
thelocus of syntacticformation rules and the insertionof lexical items. Crucially, the derivational rules that connectS-
structure to LF are without visible consequences: they perform“covert”movementsthat account for the mismatches
between interpretation and surface form.
The most recent variant, the Minimalist Program, responds to the attenuated roles of D-structure and S-structure in
Government-Binding Theory by eliminating them altogether. Syntactic structures are built up by combining lexical
items according to their intrinsic lexical constraints; the operation of combining lexical items into phrases and of
combining phrases with each other is called Merge. Merge operations can be freely interspersed with derivational
operations. However, at some point the derivation splits into two directions, one direction (“Spell-Out”) yielding PF
and the other LF. Despite all these changes,