"This was done under the assumption that the car is blue"


"This was done under the assumption that the car be blue" ?


  • 1
    Perhaps someone else can provide an authoritative explanation as to why only format #1 is likely to be accepted by native speakers. In certain contexts you might read something like "...the principle that they be treated with respect" (note that assumption, belief, principle, etc. are syntactically equivalent in such constructions). But that's a rare usage which is unlikely to concern the average learner. Oct 31 '13 at 21:24
  • I would also accept "... under the assumption that the car was blue." Unless you're speaking pirate ;-) "Aye, Blackbeard, 'twas done under the assumption that the car be blue."
    – Jim
    Nov 1 '13 at 4:04
  • I vote for @FumbleFingers's comment. The word "assumption" is generally followed by a kind of fact, a kind of condition. So it should be the 1st one, not the 2nd one that states a "to-do" thing (that the car should be blue). Unless, like Jim said, you're speaking pirate. :)
    – Safira
    Nov 1 '13 at 5:22
  • @Jim, Safira: Uneducated or "pirate" speech aren't the only credible contexts, as the link in my first comment shows. Personally, I think it probably is grammatically "valid" to use plain be here - either as a "subjunctive" form, or with an implied preceding will/would/should that's been "deleted". It's a rare form, and not something a learner should want to assimilate and repeat in other contexts, but that doesn't make it "wrong" in strictly grammatical terms. Nov 1 '13 at 13:46

The subjunctive is not required here. And in fact, it should be:

This was done under the assumption that the car was blue.

because the doing and the assuming and the car's being blue were all going on at the same point in past time. (Jim says he would "accept" was, but I'm going a step further and saying was is correct, and is is not correct.)


This is a really difficult one to explain because it depends on what you might mean by "under the assumption", which is a polysemous word, which means that it has multiple definitions. I would say it this way:

This was done under the assumption that the car would be blue [when I received it.]

What do you want to say here? Here's an example of the subjunctive with "assume". It is used normally with the past subjunctive (although the present subjunctive is possible, but very formal/archaic) when "assume" means "imagine/suppose". Example:

Assume I were a space alien. What would you think of me then?


Assuming [that] the house were for sale, would you buy it?

I think in the above situation, you want "under the assumption" to mean "provided that" or "if" or "assuming that". In the future tense (or construction if you should be one who believes English has no future tense), it would be correct and very formal to write it this way:

This will be done provided that the car be blue" or "under the assumption/condition" that the car be blue.

I would stay away from your example or use "would be" after the "the car"; however, it could be "was" there as well. It really just depends on what you might be trying to say herein. It is confusing without context clues.

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