It's hard to classify aspectual "would". It only occurs in the past 
tense, so there is no opportunity to test it for 3rd-person present. 
And expressions like "had would" (cf. "had eaten") don't occur. "Is/was 
willing" has nothing to do with habits. I don't detect any trace of 
either deontic or epistemic meaning in this use of "would"; it simply 
describes a past habit factually. The fact that sentences with it are 
ambiguous out of context has no impact on the analysis; that is true of 
any homonym.

I'm not sure why, but I think of the past-habitual "would" as coming 
from the past tense of "will". We project future habits with "will", 
though this appears not to be a special case; it's just the usual 
future: "When I move to the Virgin Islands, I will go sailing every 
day." The origin might be traceable or commented on in reference works.

  Paul's questions about "used to:

1. Isn't this a replacement for the old verb, 'wont', as in "He was 
wont to do it."?

This is unlikely, since "use" as a verb for habits was in use at the 
same period as "wont to do it".
   
2. Why do we use the past form even in present expressions ("I am used 
to it.")? The same is also true with 'supposed to', which students 
almost always mis-write as present in form.

We don't.  The "used" of "I am used to it" is participial; "used to it" 
is a subject complement modifying "I".  We never use "use" in the 
present tense to reflect habits:

1. *I use to run every day. (We say "I run every day"; simple present 
tense is the habitual aspect marker for non-state verbs.)

Future is also impossible:

2. *When I move to the Virgin Islands, I will use to sail every day."

When we negate, the tense marker moves, as it should, to the AUX:

3. You didn't use to drink so much.
4. (British) You usedn't to drink so much.
5. You used not to drink so much.

If I recall correctly, Huddleston & Pullum refer to spelling confusion 
in cases like this, so that some people write "usen't to" and some 
write "didn't used to". This is perfectly logical, given that the verb 
has fossilized -- people aren't sure how to spell it, because it is no 
longer functioning regularly.

As to "I am supposed to", I imagine this has its origin in a passive 
(people suppose that I will ... ), in which case it is again not a past 
form. It's a participle.
 
Johanna Rubba, Assoc. Prof., Linguistics
Linguistics Minor Advisor
English Department
Cal Poly State University
San Luis Obispo, CA 93047
Tel. 805.756.2184
Dept. Tel. 805.756.6374
Home page:
http://www.cla.calpoly.edu/~jrubba
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