Can / Could and Will / Would

Note 1. If we disallowed tense completely in modal verbs, we would be unable to distinguish between these two sentences: 1. 'JT says you can't make it.' (Never mind.) 2. 'JT says you couldn't make it.' (Why was that?)

You are right to say that we cannot distinguish between the two sentences, where semantic tense is concerned. The truth of the proposition with respect to speech time cannot be ascertained. The different forms of 'can't' and 'could' are those of syntactic tense, not semantic ones. Your interpretations of the two sentences as disambiguated by your bracketed replies give no reference to the tensal qualities of the previous sentence.

Note 2. These sentences, meanwhile, would apparently be tenseless: 'I can't do it.' 'I couldn't understand it.' 'I couldn't help myself.' 'I can't explain.'

Rightfully, they are tenseless. Semantic tense resides in the context of discourse. So:

(1) I can't explain it to you even if you wanted me to.
(2) I couldn't explain it to you even if you wanted me to.

Both are grammatical without any reference to tense, i.e. (1) is not semantically present and (2) is not semantically past. I'm not saying that modals cannot bear semantic tense, but it does not have to, and it doesn't unually do. Main verbs usually bear tense, for lack of that, speech-time reference is drawn from context.

eq

Hmmm... I will try. A single example is insufficient proof to prove a hypothesis. The converse is also true, where a single counterexample is insufficient to disprove a hypothesis.

An example: We form a hypothesis stating that to form a basic english plural is to suffix an /s/ sound to a noun. Cats, rats etc. And then we notice that we have plurals sheep-sheep, goose-geese. Do we abandon our hypothesis that plurals are formed by suffixing an /s/ because of these counterexamples? We cannot tell until we collect more data. We will then find that overwhelmingly, plural nouns do suffix an /s/, and these foot-feet, goose-goose examples are irregular; thus we maintain our hypothesis that plurals in general suffix /s/ but we also include a set of irregularities and the environments those occur in.

Does this make more sense?

1. 'Last week, I may go sailing.' I find this sentence baffling: it seems to contradict itself. The contradiction seems to reside in the opposition of 'may' and 'last week'. I myself would describe this as a conflict of context (past) and tense (non-past). How would you describe it?

The cotradiction lies not in tense, but in the application of modality. The modal 'may' can roughly be translated to mean "there is a possibility that". Even if you had uttered "Last week, I might have gone sailing"/"Last week I might go sailing", it would still be semantically strange. "Last week" defines your time-frame, which is in past time. So, for all purposes of discussion, barring amnesia or something, you already know the outcome of the possibility of going sailing. So stating that "there is a possibility" which translates into uncertainty, is rather odd.

So, to utter sentence 1. would not be grammatically incorrect; it is perfectly well-formed, but semantically unsound. To make it semantically sound, you would use "would":

1a. Last week, I would have gone sailing but it rained.

Assuming you were to utter:

1b. *Last week, I will go sailing.

This would be ungrammatical, but not ill-formed syntactically but semantically coherent because the modal will express modality, not tense. Consider:

2. Last week, I wanted to go sailing.

Now, here you still have a past time frame, but you have a present-tense verb. This is because the infinitival-to clause "blocks" tense agreement on the main verb. So syntactictically, the main verb is in present-tense but semantically, it still is in past time.

It seems to me that the arguments that have been used to demonstrate that modal verbs are tenseless could also be used to demonstrate that non-modal verbs are tenseless. How then may we demonstrate that, on the contrary, non-modal verbs do carry tense?

I've been talking about syntactic and semantic tense here and there but I think I have failed to explain what I actually mean. I will assume by non-modal verbs to mean main verbs and not auxiliary ones.

Syntactic tense is simply the agreement on a verb. This can be due to overt or implicit factors:

3a. I go to the market.
3b. I went to the market.

The only difference in these sentences are the main verbs. Here, the motivation for the tense change is due to the fact that you want to express an event that took place in past time. This is semantic tense: the event with respect to speech time. Now consider:

4a. I went to the market and bought some vegetables.
4b. I went to the market to buy some vegetables.
4c. I went to the market with the purpose of buying some vegetables.

Here we see the main verb in its various forms, but all referring to the same event, that is: buying vegetables at the market. Therefore the past, present and progressive forms don't actually refer to the past, present and progressive per se, but because the verb "buy" is uncontrolled in 4a, to-controlled in 4b and of-controlled in 4c. This is what I mean by syntactic tense.

To demonstrate that main verbs to carry tense, we can refer to 3a and 3b. There is no other way of expressing different semantic tense other than by using the past form of the verb.

5a. I can go to the market.
5b. I could go to the market.

Despite the different syntactic-tenses on the modal, neither 5a or 5b gives the interpretation that 'go' is in past time. In some languages like Turkish, modals of necessity (must, shall etc) are simply inflections. In Chinese which is uninflected and therefore do not have tense, the "tense" of the entire proposition depends on whether a time marker has been specified.

On the question of 'proof' and 'hypothesis': the position on the one side is that 'all modal verbs are always tenseless'; on the other, that 'modal verbs are sometimes tenseless'. The analogy with plural forms would be with one hypothesis that stated that 'all plurals were formed by adding S', and another that said that 'plurals are sometimes formed by adding S'. It would suffice to find one example of a plural form that didn't have an S to disprove the former hypothesis, and prove the latter.

That is correct. However, if someone comes along and asks you how to form English plurals, you would probably say, "add an -s behind". Then go about describing the irregularities. What I want to say is that there are few rules in languages that are absolute. It all depends on what the regular trend is and that trend is adopted as a rule, with the exceptions wrapped around. Learners (EFL and ESL) included then abstract from these rules, then memorise the irregularites.

eq

1. 'The modal 'may' can roughly be translated to mean "there is a possibility that".' If 'may' contains 'is', does that 'is' not denote present-ness?

I'm afraid I will have to be abit technical; my apologies if it puts anyone off. The translation of "may" is actually a logical one. In formal semantic theory, it would be known as an "epistemic possibility operator". Judging by your nickname, I would assume you love technical things (correct me if I'm wrong):

let proposition P = "I go sailing".

Now, modals like "may" (according to common theory that is) is a function. Not unlike your math functions, which take arguments. So, in a sentence like "I may go sailing" will be represented simplistically as such with the arrow -> meaning "implies":

may(P) -> (there exists an event e, such that the probability of e=P is greater than zero)

It's actually much more complicated than this but this will suffice for the discussion. Now, "last week" is what is called a temporal operator. It moves the event in time. So:

Last_week(P) -> (there exists an event e in time t, such that t=(7 days before speech time) AND e=P is true)

2. '...if you had uttered "Last week, I might have gone sailing"..., it would still be semantically strange.' In another post, another member (Just The Truth) also commented on the strangeness of 'might have', in a similar context. I don't myself find it strange:

Before I answer this question, let's look at the logic of "Last week I may have gone sailing":

Last_week(may(P)) -> (there exists an event e in time t, such that t=(7 days before speech time) AND the probability of e=P is greater than zero)

Perfectly fine. The disjuncture lies not in the semantic logic, but in the fact that if you spoke of a past event, people assume that you already know the outcome of e=P (whether it is true or false). So it may seem odd to imply that you don't know.

Now I will answer the question with respect to your interpretation:

[I might have gone sailing last weekend.]1 [But I didn't.]2 [And it was all because of you. You said we had to visit your mother]3

The square bracket bits are the three parts of the logic, the event, the outcome and the causality (or what is called the entailment).

The Event (1): Last_week(may(P)) -> (there exists an event e in time t, such that t=(7 days before speech time) AND the probability of e=P is greater than zero)

The Outcome (2): e=P is false

The Entailment (3): You visiting your mother ENTAILS that you could not have gone sailing because you cannot be at two places at once.

So, if you extract these bits of information from "Last week, I might have gone sailing" it would be totally fine. But this is a result of two things, knowing the outcome (that you didn't go) and the entailment which is derived from context.

If the hearer only extracted infomation leading up to the event but without the outcome or the entailment, then it would seem odd. The hearer would be waiting for the rest of the information. If you don't provide it, then the disjuncture occurs.

b) 'I might have been a contender.' (It is no longer possible.)

The same explanation applies here. The hearer wil be waiting for information that can either be supplied by you or by the context of discourse. If you went up to a complete stranger and said this, they might ask "to what?", "when", "so you are not a contender now?".

c) 'Who took my rugby boots?' 'I did, I'm afraid.' 'Well, what a nerve. You might have asked.'

Things are different here. This is a matter of the pragmatics of the utterance, which deals with language use. "might" here is not a possibility operator; you actually want to say that "It was his obligation to ask you". Even saying "you should have asked" is hedging and being polite. Another pragmatic issue is what you have mentioned, that "might" seems to carry along with it a connotation that the outcome of the possibility failed. You have said it yourself:

While 'might' sometimes denotes a past possibility that is no longer a possibility (i.e. 'there was a possibility'):

I don't think it's a BrE thing, I would think all native speakers would behave this way. It's lik how me learn to say "could you pass me the salt?" when it's not a question but a polite form of the imperative "pass me the salt".

3. 'Last week, I wanted to go sailing.' 'Now, here you still have a past time frame, but you have a present-tense verb.' I'm slightly puzzled by this – isn't it a past-tense verb ('wanted')?

I'm sorry! I was referring to the verb 'go' not 'wanted'. The verb is dominated by the infinitival-to which blocks it from taking syntactic tense but still under the scope of the time frame "last week".

eq

How would we know which was which?

We don't, where the logic is concerned they are synonymous, hence the argument that modal don't bear semantic tense. It of course does not preclude the extraction of contextual information from either through the discourse or through "quirks" of the language.