Does 'would' sometimes substitute other modals?

Question

Without you, I couldn't have done it.

Without you, I wouldn't have done it.

Is there any meaningful difference between those two above? In my humble opinion, the first one sounds as "I wasn't able to do it, and then you showed up before me." On the other hand, the second one sounds like "I didn't even attempt to give it a try until you showed up."

However, some of websites hiring native-Eng people, which give English translation services in my country, put the word 'would' for almost everywhere too often. The very reason I showed the examples above is that they translated a sentence (it meant the first example above in my own language) into the second one in English.

They clearly stated that their translation would be incorrect because their men are not professional, though. Anyway which is correct? Please teach me.

Answer 1

Modals are "flexible" in English for two reasons:

• Many times, the literal meaning of modals is not the real meaning that the speaker/writer wants to convey.

• Much of the meaning of modals depends on the information the speaker/writer has or the way the speaker/writer is looking at things.

Would is related to will (intent/desire or prediction), and could is related to can (ability).

But a speaker may choose to use could instead of would to avoid sounding like they didn't want to do something (it's more polite to be unable to do something someone else wants then to not desire to do it).

The "prediction" meaning of would X is used instead of could X if X is 100% certain to happen. If there is only a chance, could or might is better.

That is unsafe, that platform would fall down if someone stepped on it.

That is unsafe, that platform could fall down if someone stepped on it.

And of course, if the speaker is unaware that conditions are such that the platform will fall down if someone steps on it, but does believe it is a possibility, he/she may say could instead of would since that's all he/she knows.

And because of this sometimes could is used instead of would to soften statements or avoid liability.

Answer 2

You are on the right track. In the first case, the speaker is saying I COULD NOT have done it - the speaker was unable to.

In the second case, the speaker is saying I WOULD NOT have done it - the speaker may or may not have been ABLE to, but either way, simply would not (for whatever reason) have done it.