When to use would and when to use could

To make things more clear:
Would is just the past tense of will;
could the past tense of can.

"Would is just the past tense of will"

I don't beleive that it is proper to say that a modal has a past "tense." Modals can not be inflected for tense.

"Will" and "would" are modals of volition/prediction. "Would" is sometimes a modal that corresponds with "will" but refers to past time...but it is not a past tense form of "will."

"Will" is also used to refer to future time as English does not have a future "tense," strictly speaking.

Lets see...what else? "Would" and "could" are used in "unreal" conditional sentences such as:

I would run in the marathon next week if I could . = I can't run in the marathon so I won't.

Note that "would" is in association with an event in future time in this instance...

Jim wrote:
I'm not sure anyone has actually compiled a set of "rules", but note that "could" often means "would be able to", so in a way "could" sometimes contains the meaning of "would" within it. "could" cannot always be paraphrased this way, but it very often can.

I thought I could do it. = I thought I would be able to do it.


I respectfully submit that you have misanalysed this, Jim.

does not mean or .

equals . is simply a reporting mechanism.

I thought I would be able to do it. = I thought, "I will be able to do it".

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Cacarr is dead on with her/his description of the modal as not having past tense. Sure, is used in past time situations, but so is ;

----------------
That flight will have already arrived.

This request is in the form of an Information / Pro-Forma
pack which your organisation will have already received.

Everyone Will Have Already Seen This But I Thought It
Was Funny ...

The families of those who have already died or been injured will have already
been helped by the 3 Service Benevolent Funds
-------------------

The modal auxiliary verbs, which can operate in any tense/time situation, can only be one thing, tenseless.

I respectfully submit that you have misanalysed this, Jim. does not mean or .

Terry,

Could you, (i.e., Would you be able to), show me where in my post I said either that "would" means "could" or that "would" means "be able to"? Because if you can, then you must not be able to read and understand English very well.

The use of "respectfully" in this context is, pragmatically, a sign that you do not mean any respect whatsoever.

I respectfully submit that you are an idiot.