When should I use "presume" and when should I use "assume?"

November 5, 2004 10:54 AM

When should I use "presume" and when should I use "assume?" Or are they interchangable?
posted by davebug to Writing & Language (10 answers total)

Let's think this through:

- presumption - an assumption that is taken for granted
- assumption - a hypothesis that is taken for granted
- hypothesis - a proposal intended to explain certain facts

So you can assume that certain things are true, and from that assumption, certain facts can be inferred. However, presuming that assumption might be premature and irresponsible. Maybe we can say that to presume is to state a truth with little proof other than our own hubris to do so.

"Dr Livingston, I presume." When encountering a rare and random European in an otherwise African setting, you can only presume that this European has to be the only Africa-associated European you know. You're going out on a limb, basically. You might be right, but you might not be and your presumption indicates that you really don't care either way.

Of course, "assume" has the notoriety of making an "ass" out of "u" and "me." The safest bet with assume is to reinforce an assumption with something factual. Something like, "Joe drank way too much last night and we know he can't handle his liquor, so we can safely assume that a hangover will keep him in bed until noon." Two facts lead into (and support) the assumption.
posted by grabbingsand at 11:17 AM on November 5, 2004

Columbia Guide

Personally, my ear doesn't have any good intuition about the word "presume". I don't use it much. However, this source seems to think that in this particular sense the words are interchangable.
posted by stuart_s at 12:17 PM on November 5, 2004

I have no authoritative reference, but, colloquially, I'm with grabbingsand. I've always used "presumption" to mean a riskier, less defendable or less certain kind of "assumpton". Hence, to "assume" is a neutral or unbiased notion, whereas to "presume" implies a preference, bias or agenda.

I'd be happy if someone more learned corrected me, though.
posted by normy at 1:16 PM on November 5, 2004

Checking no references, but merely going on my gut feeling, assume seems more backward looking to me than presume.

I make a background assumption about the state of things and then proceed to conjecture about something else.

When you are in court you are presumed innocent, then the facts are sorted out and we make up our mind if we think the preponderance of evidence refutes the presumption.

Our local language mavens will probably have a better answer though
posted by Quinbus Flestrin at 3:18 PM on November 5, 2004

So a presumption is an assumption of a hypothesis of an explanation? I get it.
posted by MrAnonymous at 7:27 PM on November 5, 2004

I use 'presume' because there are so many stupid people in the world who cannot resist reciting the 'makes an ass out of u and me' thing whenever they hear 'assume.'
posted by bingo at 9:14 PM on November 5, 2004

I look at it like this:

presume: a preliminary conclusion that is pending future expected information. "Dr. Livingstone, I presume." Or being "presumed innocent until proven guilty.

assume: a fuzzy conclusion based on the facts at hand, even though the facts available are not enough to be truly "conclusive". you aren't expecting future information, you just "assume" you are correct and move on. (and potentially make an ass out of u and me).
posted by 4easypayments at 9:57 PM on November 5, 2004

presume makes a president out of u and me.
nice answer 4easypayments.
posted by seanyboy at 1:18 AM on November 6, 2004

How should I presume?
posted by kirkaracha at 2:54 PM on November 6, 2004

It's a fine distinction, but I think 'presume' carries more of an air of provisionality. Thus 'presumption of innocence' (liable to be corrected in the light of further evidence), 'heir presumptive' (may not inherit after all if another child is born), 'Dr Livingstone, I presume?' (politely waiting for Dr L. to confirm his identity, instead of jumping to conclusions).

In other words, 'presume' carries the implication 'but of course I may be wrong' whereas 'assume' carries the implication 'I think I am probably right'. Thus: 'Not all the votes in Ohio have been counted yet, but I think we can safely assume that Bush is heading for victory.' Or: 'Don't be so quick to assume that O.J. Simpson is guilty of murder! I agree the evidence points in that direction, but if a man has not been convicted in a court of law then it is only fair to presume him innocent.' Or: 'I assume you'll be on holiday next week' (you will be, won't you?), as opposed to 'I presume you'll be on holiday next week' (but please correct me if I'm mistaken).

But as I say, it's a fine distinction, and in practice the two words are probably more or less indistinguishable.
posted by verstegan at 5:58 AM on November 7, 2004