grammar rules behind bare infinitives

I have so far compiled a rather long in-depth description of what and where bare infinitives are used, but my boss isn't at all satisfied. Like the previous time with "at" and "in", he says there is a MUCH shorter answer, a REASON why some use to, and some do not.

This problem just refuses to go away. I can't for the life of me get to even a half solid conclusion.

I tried explaining that inert perception verbs, modal, causative verbs, etc etc are used with bare infinitives. But that only explains WHEN it is used, not WHY it is used.

This is what I got so far, could anyone please review and see if what I've done has been nothing but a waste of time? Or make me happy and say I'm getting warmer?

Bare infinitives are used with
-inert perception (5 senses) verbs
-Causative verbs (have, make, let)
-modal verbs (except ought)

+ must be in an active voice
+ Verb is in base form
+ can be in a simple form or -ing form

(for "get", only if replaceable with "have")

Or have I left out about a thousand other things?

[Casiopea]

Alright, I'll try to make sense of it and condense it into something shorter and simpler for middle school students to understand. boy, this is hard...

I'll be back later to ask more. :P

"they're compatible with like objects"

what do you mean by like objects?

Also,
[2] I made you | wash the car.
"you" doesn't functions as the subject of "wash". "wash" lacks a subject. That's why "to" is not required.

I need to know WHY "you" doesn't function as the subject of "wash". Only cause "made" is a causative verb? Just like "let's"?

[Casiopea]

I must say I see the logic, but way complicated. Now it's getting even harder to make it concise enough for midschoolers...argh!

But hey, your explanations have been awesome, casio. I really appreciate it. :):)

I'm gonna work on it till tomorrow morning, so I'll prolly ask another q (or two) again soon. :)

[Casiopea]

Middle school? "Agh," is right. Let me do a bit of research, and I'll get back to in an hour or so, OK? I'm sure we can make this easier.

[Casiopea]

Try here:
http://www.edufind.com/english/grammar/inf2.cfm

We're dealing with catenative verbs: verbs that take a verbal object, like would go, hear . . . sing, made . . . do, help . . .find, and so on. The latter three are separated by a (pro)noun, and that (pronoun) functions as the semantic agent of the bare infinitive.

a. Modals do not inflect for tense, number or person, so their objects do not inflect (i.e., bare infinitives lack inflectional properties). "had better" and "would have" also express modality, so they require a bare infinitive.

b. With verbs of perception, e.g., I heard her sing/singing, the object "her" functions as the semantic agent of "sing/singing". "heard X DO" (Catenative) Test: I heard her. She sang/was singing.

c. Causative "make" and "let" follow the same basic pattern as perception verbs. e.g., I made her sing. TEST: She sang.

When a verb requires another verb as its object, the first, or main verb carries inflection. The second verb does not. That's why "to" is omitted. If the second verb belongs in a clause of its own, e.g., I asked her to sing (Direct Object), then quasi-inflectional "to" is added to show the verb "asked" doesn't take a verbal object. On the contrary, it requires a nominal object: the entire string "her to sing" functions as the direct object.

Special Note, the (pro)noun can be omitted, e.g., I asked to go, making it appear as if the verb "ask" requires a verbal object direct object, but that's not the case: I asked [reflexive, for me] to go.

Other:
"ought to" is a quasi-modal, like "supposed to". Note inflectional -ed.
"get" when synonymous with "have" expresses a causative meaning. See causative verbs.

I hope that helps.
All the best,

That helps a great deal, casio. Thank you very much!!

*sigh*.. trying to explain all these to EFL midschoolers here in Korea... not an easy task. I'm STILL trying to make things sound easier, and I think I've gotten it tamed quite a bit. Hope it will still make sense in the end. :)