As (29) illustrates, at LoT a structure is built up by the external merge of
semantic features in accordance with the thematic hierarchy and sent out to the
Conceptual Interface.
(29) Language of Thought
a. √hit <ag, pat>
b. Thematic Hierarchy: Agent > Patient
c. [√hit √Jane
On the contrary, at LoC in (30) semantic features are directly sent out to
the Communicative Interface, but as the thematic roles are not interpreted by
hearers, some kinds of devices to identify thematic roles such as morphological
case and functional projections are indispensable. Then, for example, FPs and
syntactic movements (external merge and internal merge) are obligatory in PDE
as in (30a), while postpositions play a signifi cant role in identifying thematic
roles in Japanese as in (30b).^24
(30) Language of Communication
a. [FP Jane
b. [VP Jane ga<ag←ga> [V’ Tom wo<pat←wo> tataita ]]]
To put it briefl y, it is considered that case exists for the purpose of the visibility
of thematic roles at the Communicative Interface. The ways to make them vis-
ible are selected in the course of derivation at LoC and are synchronically and
diachronically various depending on languages. In other words, languages keep
changing adaptively at LoC. In addition, the explanation above suggests the
possibility that language phenomena can be explained without mentioning
controversial grammatical relations such as a subject and an object.^25
Figure 13.3 The Dynamic Model of Language
Feature Selection(E-Merge)Language of Communication (LoC) Language of Thought (LoT)
(Lexical Insertion, Phonological and TRANSFER
Morphological Realization, Functional
Projections, Displacement, E/I-Merge, etc.)SEM2 Communicative Interface Conceptual Interface SEM1208 Michio Hosaka