Is it "close-minded" or "closed-minded"?

Solution 1:

Close-minded was first, but closed-minded is dominant:

Here's the earliest close-minded reference I can find from a Narrative of a Journey in the Interior of China, by Clarke Abel, 1818:

I found closed minded back to 1913 in The Century Magazine:

Edit:
After considering @FumbleFingers' comments here and his subsequent answer, I have to agree that most of the earlier close-minded references found through Google Books (including the one above) are using close |kloʊs| in this sense (from NOAD):

• not willing to give away money or information; secretive : you're very close about your work, aren't you?

This is also proven by this definition of uncommunicative from John Craig's A New Universal Etymological Technological, and Pronouncing Dictionary of the English Language, 1859:

It seems the phrase was once a common description for someone who "kept their own counsel"—usually used as a derogative, but sometimes as a compliment.

However, I did find this earlier use of close-minded specifically to mean the opposite of open-minded from an 1898 issue of The Outlook:

I also found evidence of a shift towards this sense of close-minded in other writings by the early 1900s. So, to conclude, I think the only thing new about the confusion evident by the 1960s was the frequency of the two terms in print. I realize this may not ultimately answer the question, which is correct, but the timeline seems significant to me.

Solution 2:

I understand closed-minded to be a description of mentality, without reference to any past or future changes in mentality. That is, in contrast to the argument made in the question, I think the mind is open or the mind is closed. If your mind is closed, you can open it, and then it will be open. Conversely, if your mind is open, your dealings with the interminable idiocy of modern life may close it, and then it will be closed.

I would understand close-minded to be a minor mistake or valid but uncommon* variant on closed-minded. So unless the context made me re-evaluate it I would simply assume the intended meaning was the same.

If I wished to refer to a change in mentality I would use a more explicit form.

Having said all that, I think your argument for close-minded makes perfect sense; I just don't hold to its central premise. We may have a different understanding of the terms themselves, but I think it's at least as likely that we simply have a different understanding of the mind.

(*) Note that there seems to be a difference in frequency of use between British and American English—as a Brit I rarely, if ever, see close-minded.

Solution 3:

I'm not sure it makes too much sense to ask which version is 'correct' here, but let's just have a closer look at what's going on...

First, here's my NGram

There are a very few earlier uses, but they're mostly for close-minded in the sense of reticent, unforthcoming, rather than unreceptive to new ideas which we're interested in here.

The new usage suddenly started appearing in the mid-60's, when psychologists and 'pop science' authors in the "flower power" era had more need to reference this newly-interesting phenomenon.

It's my opinion that closed-minded was the original term used by those specialists and fellow-travellers, because semantically it fitted the bill better - and avoided confusion with the rare earlier usage. But over decades the term has spread to more general use, and laymen instinctively don't much like the repetition of past-tense suffixes.

I also suspect that psychologists in general may tend to have abandonned the term in favour of more abstruse 'medicalese', which would account for the rather odd graph shape. Closed-minded will probably die off in future decades, but it will stagger on for a while on the back of a few closed-minded psychologists, and a few laymen still reading old books.

TLDR - If you want to ride the wave of the populist future, go for close-minded. If you want to be accurate, buy a medical/psychiatric dictionary and use whatever words they do now.