Landau (2010) attempts to give an argument that implicit arguments must be represented syntactically. His argument mostly uses a construction he calls find-it-Psych-Adj, illustrated below:
(1) The Professor found it annoying to listen to that speech.
As Landau shows, the subject of find is interpreted as the experiencer of the psych adjective, in this case annoying. It is this implicit experiencer that then controls the PRO subject of the infinitive (to listen to that speech).
What is interesting about this construction, not noted by Landau, is that it has all of the properties of Obligatory Control. First is the obligatory coindexing: the subject of find must be identical to the experiencer of the psych adjective. Second, as Landau shows, the implicit argument cannot be spelled out:
(2) John finds it amusing (*to him) to watch the prisoners suffer. (Landau 2010, ex. 38a)
As Landau shows, this is not true of a finite complement to find, just as it is not true of finite complements of control verbs:
(3) The researcher found that it was annoying to her/the subjects to have to hear the instructions again.
(4) compare control:
a. Billy hopes (*him/his friend) to become Captain Marvel.
b. Billy hopes that he/his friend will become Captain Marvel.
Third, only sloppy readings are available in ellipsis:
(5) The professor finds it amusing to race ants, and his assistant does too. (only, amusing to the assistant)
This is not true of finite complements to find, which allow strict readings:
(6) The professor found that it is amusing to him to race ants, and his assistant did too. (either, amusing to the assistant, or amusing to the professor)
Fourth, this construction only admits de se readings, just like control. The usual context for this involves an amnesiac war hero. Suppose this amnesiac hero is watching a TV show about his own exploits, but doesn't realize that the person he sees on the TV is him. He sees that the person on TV is embarrassed about discussing his own exploits. The following cannot describe this scenario:
(7) The amnesiac finds it embarrassing to discuss his war exploits.
The sentence in (7) requires belief de se, which is missing from this context. In contrast, a finite complement to find does not, and is felicitous in this context:
(8) The amnesiac finds that it is embarrassing to him to discuss his war exploits.
The overt him can refer to the person the amnesiac is watching on TV, without him realizing that it is himself. This is exactly like control into non-finite clauses versus overt pronouns in finite ones.
So, it appears that the relation between the subject of find and the experiencer of the psych adjective is one of obligatory control (which must be exhaustive, and cannot be partial; see Landau 2000). If all obligatory control is control of PRO, then the implicit experiencer of the psych adjective must be PRO:
(9) The amnesiac1 finds it embarrassing PRO1 [PRO1 to discuss his war exploits].
This is interesting in its own right, because PRO is generally restricted to subject position in English. But it also severely weakens Landau's argument that implicit arguments must be syntactically represented, because for the purposes of this argument he was excluding PRO. Most researchers recognize the syntactic reality of PRO, and basically view it as an unpronounced pronoun. PRO can participate in all the syntactic relations that an overt NP can; so it is not surprising that the implicit experiencer of the find-it-Psych-Adj construction can. What Landau really needs to make his argument go through is an implicit argument that his diagnostics classify as ``weak,'' but which can nevertheless do partial control. (Personally, I am not convinced that there are any ``weak implicit arguments'' in English).
One last comment on Landau's theory: In his theory, strong implicit arguments have D, but weak ones do not. This makes weak implicit arguments unable to serve as the subject of a secondary predicate, because, according to Landau, only NPs with D can be arguments. But then how could a weak implicit argument be an implicit argument in the first place? By definition, an implicit argument is an argument, of some predicate. This part of Landau's account appears to me to be inherently contradictory.
Landau, Idan (2010). The Explicit Syntax of Implicit Arguments. Linguistic Inquiry 41: 357-388.
Landau, Idan (2000). Elements of Control: Structure and Meaning in Infinitival Constructions. Dordrecht: Kluwer.
Update to post (9/17/2010):
Idan Landau sends the following comments. I agree with him that implicit goals of communication verbs are convincing cases of implicit arguments that can control but not bind.
Thanks for this interesting commentary. Here are some comments of my my own.
1. The ban on lexicalization of the argument is not special to this construction. Quite a few constructions involve an implicit position which can't be lexcicalized:
a. The topic merits discussion (*of it).
b. John gave me a/*his call.
I'm not sure PRO is motivated in all of them. Just like in your proposal, the implicit position in (a) is an object position; in fact, in the find-it-Adj. cases, it's an oblique position. For PRO to occur in it would be very unusual. In fact, so unusual - also crosslinguistiucally - that this alone is a strong reason for me to doubt your conclusion.
This would imply that the signature properties - sloppy reading, ncessary se se etc. - are a necessary corollary of PRO, but not a sufficient indicator for its presence; other grammatical elements may induce the same signature. Note that simple reflexives are also necessarily sloppy and de se:
c. John hates himself and Bill does too.
d. The unfortunate hates himself.
I somehow sense that the find-it-Adj. construction involves some "complex predicate", in which the argument structures of 'find' and 'Adj.' coalesce' (note that the subject of 'find' is also an experiencer), and that this process is responsible for the effects you observed. If true (I don't know yet how to formalize this), the situation would be quite different from standard OC, where the argument structures of the infinitive and the main predicate remain distinct (ignoring the small class of restructuring).
2. There are many examples of WIA controllers in English - other than in the find-it-Adj constructions. I cite an example with 'say', and one can add other communication verbs:
a. John said/signaled/shouted (to the kids) to stay alert.
Dative controllers are easily omissible with gerundive complements:
b. He recommended/suggested/offered [filing a complaint] (to the tenants).
Experiencer arguments of adjectives are also possibly implicit:
c. It is fun/amusing/disturbing (for Peter) to watch this scene.
And so on. So I don't think your skepticism is warranted.
3. Your last comment rests on the ambiguity of 'argument'. I tried to be clear on this term, but maybe I wasn't clear enough. Anyway, the contradiction is illusory.
One sense of argument is the logico-semantic sense: an argument of a predicative function, or more linguistically, a slot in a theta-grid. This sense is completely a-syntactic, and has no implications for syntactic representation. It is in this sense that WIAs are arguments.
A second, syntactic sense of 'argument' is relevant for the saturation of secondary predicates. This is where [D] is crucial, in definining SIAs. It is an empirical observation that two such notions of 'arguments' must be entertained (the split between WIA and SIA is theory-independent). One can think of various ways to localize it in the grammar. Perhaps it is in the nature of the predicator itself - verb or adjective; maybe it is in the distinction between primary and secondary predicates; or maybe it is a by-product of a Pred head, present in secondary predicates only (and not in verb-argument combinations). Whatever the solution is, the two senses will be available in different contexts and hence would not create a contradiction.