What is the exact meaning of the phrase "could have stemmed from" in the following passage? The words in bold are intended:

The role of the Tudeh and its support of the Soviet Union's demand for an oil concession in the north or Iran were clear evidence of their closeness, especially when members of the party took to the streets in large numbers in favor of the Soviet bid. On balance, it could be argued that their support could have stemmed from a nationalist need to counter-balance Britain's predominance in Iran.

The ambiguous point is that their support was really stemmed from a nationalist need or not. Could have pp means that something was possible in the past, or you had the ability to do something in the past, but that you didn't do it. But a am not sure about this function in the above passage. I should say Tudeh was an Iranian communist party famous for supporting Russia.

  • As you say, their support is a historical fact. So I am not sure how your two options are different, or how either one applies. They did support the Soviet bid. What remains unclear is what their reasons were. That is the only hypothetical bit about the situation. And that is the only hypothetical bit that the could describes. Maybe their support was due to a nationalist need. Or maybe it was due to them really really liking giraffes. That is all the passage is saying. – RegDwigнt Jan 18 '20 at 21:57
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    Regardless of the historical record, "their support could have stemmed from X" means that it's possible that the support was a result of X, but the absolute truth of this is not being asserted. – Hot Licks Jan 19 '20 at 21:55

This usage is defined at https://www.merriam-webster.com/dictionary/stem as

intransitive verb

: to occur or develop as a consequence : have or trace an origin

her success stems from hard work

You could rephrase the sentence as

On balance, it could be argued that their support could have been because of a nationalist need to counter-balance Britain's predominance in Iran.


Close alternatives would be "might have arisen from" or "could have been caused by".

"Stemmed" is being used as a plant metaphor (like "grown" or "blossomed"). It's a verb, but a metaphoric one, so the passive "was really stemmed" doesn't really work - though the active "their support really stemmed" would.

It's not so much ambiguous as intentionally vague - the writer can't demonstrate for certain whether the support was or wasn't caused by "a nationalist need", so has left that up to the reader to infer.

  • Hi! Thanks very much for your kind and fast Answer! But, In Grammar books it is always said that could have pp refers to something in the past that there was possibility for it to be happened but it was not so. According to the passage, seemingly "could have pp" has not always such a function! Help me please about it! – Arya Jan 18 '20 at 19:05
  • @Arya - It's not always the case, but I see what they're saying. Sometimes it's implicit - "I could have fallen off the cliff" or "I could have been an Engineer" would be most likely to be said by someone who hadn't, or wasn't. It can also be used when the writer doesn't know whether something's true or not. "A cat could have walked past my window" or "The British government could have been taken over by aliens" suggests an absence of knowledge (though I'm in two minds about the second one). In the sentence in the question the writer wants to suggest it, but doesn't have evidence. – ItWasLikeThatWhenIGotHere Jan 18 '20 at 19:21
  • Dear unknown friends! Thanks very much. It was a thorny problem for me, but you, my unknown friend, solved it. Thanks endlessly. – Arya Jan 18 '20 at 19:49
  • ... it could be argued that their support could have stemmed from ...

That's two could's, one modifying the other; since could indicates possibility, but not probability, each proposition has less than .5 likelihood. Since one composes with the other, the product rule applies, and the resultant likelihood is quite low. Two propositions of likelihood .4, for instance, have a joint likelihood of .16. In effect, phrasing things this way is a polite brushoff.

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    First you say could doesn't indicate probability, then you assign specific probabilities to each use of could. – The Photon Jan 18 '20 at 22:42
  • "Possible, but not probable" means 'less than 50% probability' in English. There is a difference between the words used as modals and the words used in mathematics. Like "argument" or "function", words used in mathematics have their own rules. – John Lawler Jan 19 '20 at 0:31
  • @JohnLawler - Show us a dictionary that mathematically defines the probability associated with "could". – Hot Licks Jan 19 '20 at 21:58

Could have pp means that something was possible in the past, or you had the ability to do something in the past

No, in this case it is expressing uncertainty, as could is a strongly inflected subjunctive form of can. The subjunctive has significantly eroded in English (hence I think this question is relevant for ELU, even if your broken English would almost imply it was a better fit for englishlanguagelearning.SE). This is called potentialis, which is distinct from irrealis or the quite factual negative expressions (i.e. cannot) in past tense (could not). Adding have to form past tense makes it clear that could itself is not marking the past, as that would be redundant.

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