Verbs with sentential subjects

The following contrast involving complementizers surfaces with sentential subjects:

(557)0(557

(558)

*(That) John is crazy is likely. 

Indicative sentential subjects obligatorily have complementizers while infinitival sentential subjects may or may not have a complementizer. Also if is possible as the complementizer of an object clause but not as the complementizer of a sentential subject.

(558)0(558

(559)

S₀.t:$\langle$comp$\rangle =$ that/whether/for/nil  (559)0(559

(560)

S₀.t:$\langle$mode$\rangle =$ inf/ind  (560)0(560

(561)

S₀.t:$\langle$assign-comp$\rangle =$ inf_nil 

If the sentential subject is finite and a complementizer does not adjoin in, the $\langle$assign-comp$\rangle$ feature of the S₀ node of the embedding clause and the root node of the embedded clause will fail to unify. If a complementizer adjoins in, there will be no feature-mismatch because the root of the complementizer tree is not specified for the $\langle$assign-comp$\rangle$ feature. The $\langle$comp$\rangle$ feature nil is split into two $\langle$assign-comp$\rangle$ features ind_nil and inf_nil to capture the fact that there are certain configurations in which it is acceptable for an infinitival clause to lack a complementizer but not acceptable for an indicative clause to lack a complementizer.