"or" in English

[jack]

My impression of "or" in English is that it can mean either "inclusive or" or "exclusive or" depending on context.

Example #1:

"Are you now or have you ever been a member of a communist party?"
"Would you like milk or sugar in your tea?"
"Don't trust someone if they're incompetent or malicious."

Obviously someone who IS NOW and also HAS BEEN IN THE PAST is supposed to answer "yes", not "no". You're allowed to ask for milk AND sugar. Incompetent malicious people are not automatically trustworthy.

Example #2:

"Would you like dinner now or would you like to freshen up first?"
"Eat in or take away?"
"Would you like the free gift or the cash equivalent?"

It would make no sense to ask for both.

And some of those questions have exactly the same form, it's just that you're supposed to know from context that having both is normal, or having both isn't being offered, or isn't possible.

However, I know some people say "in English, 'or' means 'inclusive or', even if sometimes common sense/politeness/physics stops you having both options at once" and some people say "in English, 'or' means 'exclusive or' but people sometimes use it sloppily and we know what they mean".

However, I can't really see the difference between those and "it can mean either depending on context". Is there any evidence that one of those is a superior description of the "default" interpretation (not just "which is more common", but "which people understand you really mean if you emphasise the meaning of the word").

Comments

[gerald_duck]

I suspect there are worse problems with pinning down the exact definition of "or" if one looks closely; there are with most common words.

"and" has similar problems. Compare "a large and furry cat" with "a black and white cat". In the first case, both adjectives apply to the entire cat; in the second, each adjective applies to part of the cat, between them describing the whole.

[simont]

When I was quite little, and learning BASIC programming from the Spectrum user manual, I recall becoming somewhat confused when I noticed that English had the three conjunctions 'and', 'or' and 'but' whereas BASIC only had the first two. I worked out quickly enough that BASIC had no need for 'but' because it didn't mean anything different from 'and', but then I got quite puzzled about why English did need both of them in that case!

(I don't remember why I picked out those three conjunctions in particular. I suppose either I hadn't recognised things like 'because' and 'so' as being in the same grammatical category at all, or else I'd pre-filtered down to only the set that had even a chance of representability in BASIC. Take your pick ;-)

[jack]

It seems "A but B" means something like "A is technically true but the obvious implications thereof are somewhere between 'not true' and 'nearly true' because of B". Which is quite complicated, I'm not surprised it's not represented natively in a programming language :)

It depends how much the obvious implications of A are part of A.

I you say "let's go to the pub" and I say "I know a short-cut", the literal meaning of what I say is "I know a short-cut", but what I'm really saying is "let's go that way". But if I say "I know a short-cut but it's closed" the literal meaning is unchanged, but the implication is removed. So does that make the first half of "A but B" true or not? It depends whether you take A as "I know a shortcut" or "I know a shortcut, let's go that way".

Mostly programming languages don't bother with implications, although you could argue you could do something similar if you have a short construction meaning something like "all x in X are P (and there's at least one of them)" rather than "all x in X are P".

Even "because of B" is complicated to formalize, it can mean either "B causes A'" or "B is evidence of A'" and both of those are hard to formalize.

[simont]

It seems "A but B" means something like "A is technically true but the obvious implications thereof are somewhere between 'not true' and 'nearly true' because of B".

I can't not pull you up on defining "but" with a sentence involving "but" :-þ

I think the real point is that the distinction between 'and' and 'but' doesn't really have any effect on the meaning of a question – and all Boolean expressions in programming languages are implicitly questions posed to the computer ("is this complicated thing true or false?"). In a declarative statement, 'and' vs 'but' provides additional subtext along with the obvious propositional-logic value of the statement; for instance, if I say "This tastes cinnamony and yummy" versus "This tastes cinnamony but yummy", then on the face of it I'm making the same two assertions about the taste of the thing, but my choice of 'and'/'but' hints some extra information about whether I like cinnamon in general, or perhaps whether I'd have expected a cinnamony taste to go well in this particular context. Whereas if I ask "Does it taste cinnamony {and/but} yummy?", then the and/but distinction is still conveying an editorial comment from me, and the information I'm asking you to provide to me is more or less the same no matter which conjunction I picked.

So, put that way, perhaps we should permit 'but' in programming languages as a synonym for 'and' – and the distinction between the two functions purely as a comment to the reader :-)

[jack]

I can't not pull you up on defining "but" with a sentence involving "but" :-þ

LOL. Yes, I recognised the irony. However, I don't think I'm explaining "but" to someone who doesn't know what it means. I think we all know intuitively what it means, and are now trying to formalise that to a theoretical explanation. So there's no reason to avoid it :)

I think the real point is that the distinction between 'and' and 'but' doesn't really have any effect on the meaning of a question

That sounds right, but DO you use "but" in a question? What does that mean?

perhaps we should permit 'but' in programming languages as a synonym for 'and' – and the distinction between the two functions purely as a comment to the reader

That's an interesting question. I think it's often really useful to have synonyms with the same semantic content, but which convey extra information to the reader about what is the INTENDED meaning. But also can be really confusing if they're used randomly or differently in different contexts.

So if "but" would convey extra, it might be nice. But *would* you want to use it?

Something like, "if ( a is not null but a.b is null) then a.b = new ..."?

[mathcathy]

Am I being dense? I can't see at all how but means and, or how it could ever be used interchangeably. Can you give an example?

[jack]

I'm not completely sure, I don't exactly think that, so you're probably better off asking SimonT. But what I *think* it means is that, if you're thinking in terms of boolean logic, AND, OR, NOR, XOR, etc, if "I'm happy but a bit nervous" is true, then "I'm happy" and "I'm a bit nervous" are both true, just as if you'd said "I'm happy and a bit nervous". (But that ignores the difference between "and" and "but" that "but" suggests you're a bit less happy than you might be otherwise.)

[simont]

Yes, what Jack says, basically. If you say "Statement A and statement B", the (primary, simplest) information you're conveying is that both of the statements are true; and if you say "Statement A but statement B", the same applies – you're still saying that both of the statements are true.

Where they differ is in the secondary subtext, in which the use of 'but' hints that it's perhaps not what you'd expect (if A normally goes with not-B and this is a rare exception), or that the two have conflicting effects (if you think A is good and B is bad, then the 'but' suggests that B makes you less happy about A) or some other kind of opposition between the statements being joined.

You can imagine situations in which either conjunction could be used and the only difference is in the subtext: e.g. compare "He's a boy and he likes playing with dolls" with "He's a boy but he likes playing with dolls". Both are telling you the same two basic facts, but one is also commenting on the divergence from conventional gender roles (perhaps even making a negative value judgment, though that probably depends on who's saying it).

But if you ignore that kind of subtext (as a programming language would, having no use for such editorialising in the first place) then the difference between the two words vanishes, so that "A but B" tells you nothing more or less than "A and B" – just that both of A,B are true.

[mathcathy]

Doesn't but have other meanings as well, though?

[simont]

Off the top of my head, I can't immediately think of one that doesn't boil down to 'and' with added subtext. Can you?

[mathcathy]

I guess not.

I suppose I'm thinking about when a question is incorrectly begun with "but".

So when someone isn't acknowledging whatever has gone before, but is using but to argue.

"But don't you have to do that tonight?"

[simont]

Yes, I suppose that does count as different, since it's not really joining two sub-statements together at all. (You might sort of argue that it's attempting to join your question to whatever the previous person said, and hint at an opposition between those two things as I described above, but I think that would be a bit of a stretch.)

That kind of argumentative question is even more out of bounds for the sort of thing you might even try to express in a programming language, though, so it doesn't really come into the question I started with (my childhood confusion over why English needs both 'and' and 'but' while BASIC only needs one of them).

[mathcathy]

No, I think you've adequately explained why "but" and "and" are the same in a programming context. Thank you :)

[vyvyan.livejournal.com]

What about the meaning "except" e.g. "all but one"?

[simont]

I feel this post is incomplete without the following quotation:

and when Rabbit said, "Honey or condensed milk with your bread?" he was so excited that he said, "Both," and then, so as not to seem greedy, he added, "But don't bother about the bread, please."

Also, example #1(iii) amuses me due to the idea that it would become an exclusive-or, if you were to adopt the kind of definition of 'incompetent' that you might find in a Raymond Smullyan puzzle, i.e. something along the lines of 'always does the opposite of what was intended'.

[jack]

it would become an exclusive-or, if you were to adopt the kind of definition of 'incompetent' that you might find in a Raymond Smullyan puzzle

Yeah, I've met some people who seem to do the opposite of what they intend, rather than just be ineffectual, but I think SURELY it can't be consistent enough to rely on...

The evil question is also interesting. I think if someone is purely selfish, being competent is better: they CAN work reliably with other people, and if they run the country, they may see the benefits of a decent economy and have no incentive to randomly ban stuff for the sake of it.

But if someone is capricious or malicious, then everything they succeed in may make matters worse for everyone, so being incompetent is better.

[simont]

I've met some people who seem to do the opposite of what they intend, rather than just be ineffectual, but I think SURELY it can't be consistent enough to rely on...

Indeed, but exaggeration for comic effect and Smullyanesque logic puzzles are exceptions :-)

[jack]

Indeed

Yes, exactly that.

I can think of specific cases where someone may be reliably wrong, e.g. where they're quite experienced, but badly calibrated on some key piece of information. But it's still more like "right plus an error" rather than "anti-right".