^ "nah"? The answer is YES, but not the way you're using it. It is more often used as an auxiliary (also called "helping") verb just like the way you're using it, even though it's the past tense of CAN. In your example, it's an auxiliary verb. If you combine it with "[subject] could [verb]", then it's not the actual verb. If you say, however: "Yesterday, I could", then it's not a helping verb and it's on its own. You called down the thunder, well, now you got it. Can you call down the thunder? You could. http://www.merriam-webster.com/dictionary/can?show=0&t=1306987744
It's a modal modal auxiliary. Yeah I know linguistics. But you bring up an interesting point, since could is not the verb it doesn't have a tense. But the problem lies in the fact that if we have a CAN then why do we need a COULD? Get my drift?
Ah... well played. I agree. I could have gotten your drift earlier. Before, I could. Right now, I can. But, in another life, I could not have. Now, I could have. In the future, I probably would. Should I? Yeap, I could.
could is a being verb. is am are was were be being been has have had do does did shall will should would may might must can could.
Crazy Dave, you are livin' up to your name. Could is not a verb at all. If it were, like swoly said it could be conjugated. That's why this question is not easy. Verbs in the general sense are either present or past tense. Here's another brain teaser for you. In the sentence above: when I use the verb said: "it could be conjugated" is the proper way to say it. You would not say: Like Swoly says it could be conjugated, but rather it can be conjugated, meaning that the tense of the preceding verb has an effect on what version is used. That in itself doesn't make could past tense, but it certainly makes you believe that it has properties of it, linguistically speaking.
The past tense of 'can' is 'did' or 'didn't'. I can go to school. I did go to school. I didn't go to school.
This has been a pet peeve of mine for years. English is one of the few languages which use what we commonly refer to as 'helping verbs'. As Crazy Dave pointed out, we have a small handful of 'helping verbs' which are use to modify an actual verb in order to establish 'state of being'. In my mind, this is vastly superior to each verb having its own endless set of variances to establish state (I'm looking at YOU, all you foreign-languages-I-had-to-try-to-learn-in-school!). The pet peeve comes from having heard so many times from non-native English speakers that 'Ohh, English is so hard to learn! It's a lot harder to learn than _____ !'. BS. No it's not. It may be difficult to master it *perfectly* (heck how many native English speakers master it perfectly? Very few, I surmise), but it is INFINITELY easier to learn how to effectively COMMUNICATE in English, specifically because all you have to learn is that handful of 'helping verbs', a couple of tense rules for regular verbs and basic logical sentence structure, and the rest is just vocabulary. Anyway, in answer to the OP's poll, since neither 'can' nor 'could' are actual verbs as such, they are not related to each other as tenses such as can=present and could=past. They simply modify an actual verb such as 'go'. For example 'can go' indicates a state of being - (Subject) can go. This clearly defines the status of the (subject) as being in a state of 'readiness to go'. 'Could go', on the other hand, offers a subtle difference - '(Subject) could go' defines the state of the (subject) as having the potential to go at some undetermined point, which, ironically, is a future status, rather than anything having to do with past tense as the OP posits. (Clarification: by 'future status', I mean simply future status as it relates to the (subject). In other words, take the following examples: 'I can go today.' & 'I could go yesterday.' In the first sentence, the state is clearly defined as present, actual current readiness. In the second sentence, the status is defined as future potential readiness (even though it occurred in the past), so it's still technically future.. ) On another side note - take the sentences 'I can.' & 'I could.' These are not valid because they are incomplete sentences. Diagramming these sentences, you would need to supply some kind of implied verb, where it would then become something like 'I can (eat).' or 'I could (eat).', depending of course upon whatever the sentences were actually referencing. So anyway, oh well.
Can is something that you can do. Do is something you actually did. Just like in Spanish. Podar = Can, Could have, Couldn't have Hacer = Do, Did, Didn't They are certainly not interchangeable.
I was always under the impression that the past tense of the VERB "can" is "canned." Ex: "My boss canned me today because I punched my coworker in the face."
