What is the Theta Role of "It" in "It seemed that ..."

Question

How do I identify the theta role of "It" in "It seemed that there was no escape."? I understand theta roles such as THEME, AGENT, LOCATION, GOAL, FORCE, EXPERIENCER etc. However, I cannot work out what "It" would be in this case.

Answer 1

To my understanding, it has none.

Theta-roles are semantic concepts. But this "it" doesn't exist on the semantic level: it only appears because syntactically, English doesn't allow a verb without a subject.

In other words, the "it" exists only on the syntactic level and lower, not the semantic one.