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I was supposed to do my homework, but I went out clubbing instead.

On a literal interpretation, supposed to suggests that other people (or indeed, myself) might have supposed (thought, imagined, assumed) that I would do my homework. I could continue the synonyms (expected, demanded, required,...) but they're getting further and further away from the 'core' meaning of supposed.

So far as I know, the verb to suppose only has the 'duty'-related sense when used as a past participle in this way. Is this true, and if so, why?

And how come my Mum can't suppose me to do my homework? If she supposed I was doing it, that doesn't imply she instructed me to do it - just that (in the absence of evidence to the contrary) she thought that's what I was doing.

(Added later) I think all the above would remain valid and still be exactly the same question if I'd asked about meant instead of supposed.

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Related: english.stackexchange.com/questions/8129/… –  Cerberus Apr 19 '11 at 11:48
    
@Cerberus: thanks for link, but it doesn't seem to offer any clues as to why we only get this 'obligation' sense with the past participle. And it gets me even more curious about who exactly did the 'supposing', since it doesn't seem to be possible to specify that in this form of utterance. –  FumbleFingers Apr 19 '11 at 13:46
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@FumbleFingers: Absolutely true! I wasn't saying this was a duplicate; I merely added a link for visitors from outer space when I remembered a similar question. –  Cerberus Apr 19 '11 at 23:09
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the title is wrong, it should be "Why do we say “was supposed to” for “should have”?" –  Dan D. May 1 '11 at 6:37
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This is all a bit over my head, and you've all pretty well settled it, but I was thinking that the fact of someone who has some authority over one or who one wants to please supposing (believing) that one is doing a certain thing might make one feel some obligation to do that thing, thus increasing desirability of that which is supposed. –  sarah Jan 10 '12 at 15:40
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4 Answers

up vote 34 down vote accepted

This is a complicated issue, and one that is still not fully understood by linguists, or so I believe. In short: there is a tendency in many languages for words to shift in meaning between probability and desirability. This tendency is apparently strongest in certain verbs that are used without specifying who the judge is, which includes passive verb forms.


I can make a simple statement that describes a fact:

Athens is more civilised than Rome.

I can modify this to describe my attitude towards the statement. This can be done in two ways: I can give my opinion on its truth value (probability), and on whether or not I want it to be so (desirability).

  • Athens is probably more civilised than Rome. (weaker probability than when stated as a simple fact)

  • I want Athens to be more civilised than Rome. (I have added my opinion on the desirability of this statement's being true)

The desirability and probability of statements as expressed by the speaker is collectively called modality. Modal verbs generally express some form of modality (surprise!):

She goes. (no modal value, except the "default" probability value of "fact, 100 % probable")

  • She will go. (probability, very strong)

  • She might go. (weak probability)

  • She should go. (medium desirability)

  • She has to go. (strong desirability)

The problem is that probability and desirability are not always separate:

She may go.

Does this mean that it is possible that she goes? Or is she permitted to go? Permission is a weak kind of desirability: "I do not not want her to go, so she may go if she likes". Both kinds of modality are sometimes mixed up. Historically it can be seen that most if not all modal verbs have changed in their modal functions. Will once expressed only that someone desired something:

I will go.

This used to mean "I want to go"; but it has gradually acquired a sense of probability, in that it now means "it is very likely that I go" for most speakers of English, especially Americans. The other modal verbs have gone through and are still going through various other shifts.


The same can be seen in words that express some form of modality other than modal verbs. Consider the word impossible:

Now I'd like to go, Sir. — I'm afraid that is impossible. You must finish your work first.

The teacher says that it is impossible for the pupil to leave, because he does not want him to leave, and his will is an unchangeable fact as far as the pupil is concerned. But this amounts to the same as saying "I want you to stay".

Command and permission have to do with desirability: there is the thing that you desire but have no power over (plain desire), and the thing you desire and have some power over (command, permission). If you command something, you have a fairly strong desire and strong power; if you permit something, you need somewhat less power, because it will happen anyway if you do nothing, and you have a weak desire: you basically say, "you may go if you like; I don't care enough to forbid you".

The reason why command and permission are so well represented in statements of desirability is probably that it is little use stating your desires unless you are empowered to affect them to some degree, be it by commanding or begging. (Plain statements of desire do exist, though, of course.)


Now on to be supposed to.

The Carthaginian fleet was supposed to comprise two hundred ships; Scipio had hoped that there should be less, but he had to organise his fleet based on this supposition.

Here supposed to is used to indicate probability: the Romans considered two hundred a probable number.

The new ships were supposed to dominate the Mediterranean. But Rome's fleet failed her on several occasions.

Rome thought her fleet would be dominant; and she had constructed it because she wanted it to be dominant.

From here it is clear how the sense of desirability came to dominate to be supposed to. Somehow this has not affected the past participle without to be as much, and the active verb even less so.


This shift in modality can be seen in other verbs as well:

  • It was expected of Scipio that he should either triumph or perish.

  • The catapults were not meant to be transported over such a long distance.

The same type of shift can be observed in all other languages I know, in all ages. In Ancient Greek, dokeô means "to seem, appear" (cf. our words paradox and deixis); dokei moi can mean "it appears to me, that ...", but it can also mean "it seems like a good idea to ...", and hence even "I decide to ...". The personal pronoun can also be left out.

I suspect that this shift is most likely to rear its head where a verb has no agent, no person who actually does the supposing or expecting or meaning; that is why it appears first or most strongly in passive constructions. I am not sure why languages have this possibly universal tendency to shift modalities around. I don't think linguists are quite sure yet why it happens: they just describe how it happens.


On a side note, there is a general tendency for "neutral" words to acquire some sense of desirability. Consider the word shapely: one might expect it to mean "having a shape", but it now means "having a good, beautiful shape". Note that this might be emulating Latin forma, "shape, good shape", and formosus, "beautifully shaped".

But there is also high quality: originally, quality meant something like "how-ness, nature, property"; but somehow an intensified ("high") property became a good property. This process is still going on, as can be seen in modern quality shoes: without a modifier like "high" or "low", quality is now good by default. This phenomenon can be observed in many different words in many different languages. I can see why it might be efficient to use a positive sense by default if a neutral word is not modified one way or the other: it saves the speaker words, as long as it doesn't cause confusion.

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@Cerberus Wow. Sick answer. +N if I could. –  Uticensis Apr 20 '11 at 3:40
    
@Billare: Heh yeah it is a bit too long to read; I sort of got carried away... but thanks for your potential vote! –  Cerberus Apr 20 '11 at 3:44
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@Cerberus: I'm gobsmacked! That's pretty much the best answer I could imagine. You explain the processes and tendencies involved very clearly, thanks. It now makes sense to me why the meaning of words like suppose, mean, expect, etc., 'slide around'. Basically it's because they're intimately bound up with the shifting sands of probability / desirability. Which in the real world we always either get confused by, or deliberately obfuscate. –  FumbleFingers Apr 20 '11 at 3:53
    
@FumbleFingers: Exactly! The wish is father to the thought. Oh, wait, the expression should actually be the reverse. Damn, we humans have so many odd and contradictory tendencies... –  Cerberus Apr 20 '11 at 3:59
    
@Cerberus: What I particularly like about your Answer (longish, but well worth it) is that it guides me safely through historical, linguistic, & semantic issues, but leaves me free to muse (or even wax) philosophical on the probability / desirability dichotomy. If Philosophy.se ever gets off the starting blocks, that debate should be one of their big issues. –  FumbleFingers Apr 20 '11 at 4:21
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Interesting question. The short answer is that 'supposed to' is an idiomatic term derived from 'supposed'. I can't provide any evidence for the link, but it has developed two distinct meanings.

Firstly, as a synonym for 'required':

I am supposed to do my homework before watching Survivor.

Secondly, as a synonym for 'permitted':

You're not supposed to be in here!

I can only suppose (ha!) that the term originated from the definition of 'suppose' as 'theorize, hypothesize', i.e., to suggest that something is true. This true/false notion has then carried across to the idiomatic usage of 'required/not required' and 'permitted/not permitted'.

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"This true/false notion" gets even more convoluted when I consider what looks like almost exactly the same thing going on with meant as well as supposed. Where again, the 'duty' sense only seems to associate with past participle. Suppose and mean can both be related to truth/falsity, but in significantly different ways. So how come they both get dragooned into this (often unfulfilled) duty context? –  FumbleFingers Apr 20 '11 at 0:55
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I was supposed to do my homework, but I went out clubbing instead. On a literal interpretation, supposed to suggests that other people (or indeed, myself) might have supposed (thought, imagined, assumed) that I would do my homework. I could continue the synonyms (expected, demanded, required,...) but they're getting further and further away from the 'core' meaning of supposed.

I believe that there is some confusion about the core meaning of "be supposed to", FF. If I'm not mistaken, you are confusing two different grammatical and semantical meanings; the lexical verb, "suppose" and the periphrastic/semi-modal, "be supposed to".

So far as I know, the verb to suppose only has the 'duty'-related sense when used as a past participle in this way. Is this true, and if so, why?

"be supposed to" doesn't use the past participle of the lexical verb 'suppose'. It's a standalone structure that's different grammatically and semantically to the verb 'suppose'. I guess that it might have the same relationship to 'suppose' as the word 'use' in "used to + infintive" or the word 'use' in "be used to + ing" has to the verb 'use'. What that etymological connection is, I haven't a clue.

And how come my Mum can't suppose me to do my homework? If she supposed I was doing it, that doesn't imply she instructed me to do it - just that (in the absence of evidence to the contrary) she thought that's what I was doing.

You're right that your Mom can't do that because you are trying to describe a grammatical/semantical structure that doesn't exist. The lexical verb "to suppose" doesn't carry a duty related meaning.

Your Mom can tell you that "you ARE supposed to do/be doing your homework". Note the form of the 'be' verb, "are", that is required with this particular grammatical animal. The use, always, of the 'be' verb, is what makes it different from the use/meaning of the lexical verb 'suppose'.

That meaning is different from your Mom wondering/supposing whether or not you are doing your homework. This meaning of 'suppose' is "probably/likely".

The meaning of "BE supposed to" is,

"I am relating to you that you 'must' do something but the compulsive force of 'must' comes not directly from me but from another, usually/often a more powerful force."

OR

"I'm not saying you must do/have to do something, I'm telling you that someone else [or something else] says that you must do/have to do something."

(Added later) I think all the above would remain valid and still be exactly the same question if I'd asked about meant instead of supposed.

I don't understand what you are getting at here.

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I'm not at all confused about the meaning(s) of the word suppose, though I am a bit confused by your apparent attempt to convince me there are actually two different words with that spelling - one relating to expectation/duty, the other to expectation/probability. I know it's a bit long, but Cerberus's superb answer clearly shows the deep connection between these two meanings, and the way in which a living language moulds and remoulds itself around this murky aspect of human experience and interaction. Please try working through it again. –  FumbleFingers May 1 '11 at 1:54
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Supposed used as an imperative is an idiomatic pseodo-reinterpretation of its standard, predictive or interpretive use in the subjunctive mood. Its understanding as such relies on inferred meaning of words which, in common speech discourse, have come to be omitted.

You "were supposed to..." versus you "were supposed to have been..." is the key question, actually. The latter, standard, declaration, in passive voice exemplifies the correct meaning of supposed as you indicated. The truncation that led to the former derives from a tendency in speech to convert the d sound to the t sound: you were spost to.... Converting that back to writing, an acceptable spelling reattaches but not a correct pronunciation. You were supposed to... The pronunciation shift occurred and was reinforced in speech due to the juxtaposition of d and t in supposed to. There is no way to readily pronounce both consonants distinctively while, at the same time, running the two words together, as people are wont to do in conversational speech.

Linguistically, such a metamorphosis by transition from writing to speaking and back again to writing would have been prevented in the age in which ed would have been pronounced as a separate syllable: thus providing a clue as to the time before which "spost to" would not have supplanted "suppose-ed to have been."

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I disagree completely. Past perfect as opposed to simple past tense has absolutely no bearing on the probability/desirability issue so cogently explored by @Cerberus in what I still consider to be one of the best answers on the whole site. The difference in meaning indicated by a difference in pronunciation applies to other related verbs, such as have, use, as covered in that earlier question. –  FumbleFingers Nov 23 '12 at 17:55
    
Although that one was overwrought for the purpose, the pertinent part is in agreement with my insightful explanation, and not with...what is it you are trying to say? I will need to work up a new post to have space to explain in hopefully sufficient detail...a little later, as it was supposed earlier today that I would - i.e., I was supposed to - later on take someone out for supper. Please stand by. –  lex Nov 25 '12 at 3:00
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