Given an SO Σ, Search 0 picks out Σ and an element α contained in it. Then
Merge 0 applies to these objects and forms a set {α, Σ}. Let us consider the
following example:
(13) a. What did John buy?
b. [vP John [v [VP buy what]]]
The derivation of (13a) has reached the stage shown in (13b), where John has
been merged with {v, {buy, what}} to form {John, {v, {buy, what}}}. Search 0
applies to this SO and picks out what and the whole SO. Merge 0 applies to
these objects and forms the set of them. In short, M 0 ◦S 0 works as in (14).
(14) M 0 ◦S 0 ({John, {v, {buy, what}}}) = {what, {John, {v, {buy, what}}}}
The output of this application of M 0 ◦S 0 becomes the input to another applica-
tion of M 0 ◦S 0 for chain-formation (see Section 2 for details).^19
Now, let us turn to EM. Consider fi rst the cases where both of the targets
of EM are lexical items (LIs).^20 Suppose that the and book undergo EM to
form nP. So far, we have assumed that the input of Search 0 is an SO, as
formulated in (3). However, since the and book are LIs, they are contained
in the Lexicon, not in any SO. This would prevent Search 0 from picking out
these objects. Thus, it is necessary to modify the formulation of Search 0 so
that Search 0 can also pick out LIs contained in the Lexicon. A possible refor-
mulation of this operation to obtain the desired effect is the following, where
“linguistic object” is used as a cover term for both SOs and the Lexicon.
(15) Search 0 (revised):
Search 0 is an operation such that given a linguistic object Λ, it picks out
n elements contained in Λ.
Given the revised version of Search 0 in (15), M 0 ◦S 0 can take the Lexicon as an
input and pick out two lexical items LIi, LIj contained in it and form the set
of them, as shown in (16).
(16) M 0 ◦S 0 (Lexicon) ={LIi, LIj}
Thus, M 0 ◦S 0 can now construct SOs like {the, book}, where both of the members
are LIs.
However, the formulation given in (15) fails to accommodate the cases where
at least one of the targets of EM is not an LI. For example, let us consider the
derivational step where read undergoes EM with the book, as shown in (17).
(17) read ← EM → {the, book}
In order to achieve the effect of this EM, Search 0 in M 0 ◦S 0 must be able to
pick out an object contained in the Lexicon (read) and an object not contained
34 Takaomi Kato et al.