From 1896 to 1902, the Free Church Scottish theologian Alexander Whyte published a six-volume work, apparently based on homilies, describing important biblical characters:
Unless he [Moses] had had it in him, vice or virtue, to strike that bold blow at that insolent Egyptian [Ex 2.11–15], he would never have had it in him to strike off Israel’s fetters. If he had hesitated and calculated and looked this way and that way that day, we would not have had his perfected meekness before us for our text tonight [Num 12.3].— Alexander Whyte, Bible Characters, 2011 (orig.1896–1902).
Dalziel’s Bible Gallery, 1880, Plate 25. Scan: Simon Cooke.
The second sentence is a standard past closed conditional musing that had Moses hesitated rather than taken immediate action, the Exodus saga would never have been told. Yet Moses did act, and thus Whyte’s congregation and readers may contemplate Moses as an exemplar of “perfected meekness,” i.e., humility. Both clauses in a past closed conditional are contrary to fact, hypothesizing about a condition and result that might have happened but didn’t.
The first sentence, with the introductory unless clause, employs the same pairing of tenses as the second: past tense subjunctive (indistinquishable in English from the pluperfect) and past conditional mood with “would have.” While the result clause is contrafactual, the unless-clause is, in terms of the biblical narrative, true: Moses indeed “had it in him” to murder the oppressive Egyptian overseer; thus he also “had it in him” to lead the Hebrews to freedom.
The limits placed on unless in remote conditionals are thus ultimately semantic: because of the not inherent to the conjunction itself, either the protasis (unless-clause) or the apodosis (result/consequence clause) may be contrafactual, but never both at once.
This is most obvious in a sentence with unless which is not a true conditional, but states a law of nature:
Many types of fruit trees, including some apples, pears, plums and sweet cherries, will not produce fruit unless they are pollinated. — James Dwyer, John Albert, ”Dwarf fruit trees: big producers in tiny plots,” Popular Mechanics v. 147, 4 (Apr. 1977), 94.
Of the statements “no fruit” and “pollination,” only one can be true.
The Remote Exception
Although academic discourse has concentrated mostly on conditionals such as Whyte’s —and whether they are even grammatical — there are other instances of contrafactual unless worth exploring, especially since they can be rather fun.
When an unless clause is immediately recognized as contrafactual, not only is the apodosis valid or true, but the more absurd or humorous the unreal protasis, the more the apodosis is affirmed:
The seaweed salad couldn’t have been any better unless it had been brought to me by a hot naked dude. — Vegan Coach, Review of Beyond Sushi (restaurant, NYC), 6 June 2016.
She appeared to make a deliberate effort to downplay her beauty, which was impossible unless she wore a sheet that covered her from head to toe. — Sherral D. Kahey Without Probation, Parole, or Suspension of Sentence, 2012.
Unless she had flown there on wings, he could not see how Frankie could possibly have got to the Anglers’ Arms ahead of him … — Agatha Christie, Why Didn’t They Ask Evans?, 1934.
My mother normally wouldn’t have called me at that hour unless a tornado had moved through her apartment. “Gerry, I need you to come over and help me. I'm not feeling so good,” she said, and this time I believed her. — Geraldine Ferraro, Framing a Life: A Family Memoir, 1998, 172.
This construction also works in the present tense, though for this writer not as successfully:
Additionally LeBron's signature skill is probably his otherworldly passing ability, which of course would not help him in a game of one-on-one unless he were allowed to clone himself and have it still technically count as “one-on-one” because his teammate is also LeBron James. — Jack Moore, “Could Michael Jordan Beat LeBron James in One-On-One?” GQ website, 10 Aug. 2015.
Hyperbole, clones, and nude waitstaff aside, an unless clause always sets up a simple binary where either the protasis or apodosis is true or will/would occur, but never both at the same time. If the condition imposed by unless is patently absurd, the conclusion is obvious. Even a small step into the realm of the possible, however, creates enough ambiguity that a conditional must be regarded as open.
Unless they had found their way to this bank and found a place to hang on, they were dead. The stillness was so heavy he felt sure they were not alive. — Mildred Walker, Unless the Wind Turns, 1996, 220.
Are they dead or did they manage to reach the riverbank and survive? Only one of these possibilities can be true. Read further to find out which!
The Open Exception
Remote may not be the best choice of descriptors for conditionals, because if there is a possibility, however remote, that either the protasis or apodosis may be true or later revealed as such, then the conditional is not remote, but open:
If James were to die, for instance, or if he were to transfer his affections, Buckingham might well be left homeless. He would also have very little to live on, unless he had managed, during his years in favour … to accumulate capital. — Roger Lockyer, Buckingham: The Life and Political Career of George Villiers, 2014.
She saw herself hating her husband, and she knew that, unless she were careful, she would smash her form of life and bring catastrophe upon him and upon herself. So in very fear, she went quiet. — D. H. Lawrence, “Daughters of the Vicar,” Selected Short Stories, 2012. Originally in The Prussian Officer and Other Stories, London, 1914.
In the Lawrence short story, the ambiguity lasts only until the next sentence, but it is still an open conditional. Given that liquid assets and frugality were generally in short supply among the Jacobean aristocracy, the chances that the first Earl of Buckingham had much cash before his assassination are slim, but still within the realm of possibility, thus open.
Unless in Contrafactual Conditionals
Acknowledging that numerous grammarians — Quirk et al., Longman’s, Geis, Bollinger, etc. — consider contrafactual unless ungrammatical, the Japanese scholar Takao Fujita maintains in a short article that this unusual outburst of proscriptivism in the 1970s and 80s lacks basis in actual usage. The usual method of demonstrating that contrafactual unless is ungrammatical, i.e., minimal pairs where unless produces nonsense while the if…not counterpart is unobjectionable, should not be the deciding factor, Fujita says, when there are reputable authors who use this construction.
To judge by what little is available online concerning the topic, however, contrafactual unless seems to be acceptable in well-formed sentences, and the earlier discourse has apparently died down, one reason why CSEL, which otherwise takes great pleasure in debunking baseless proscriptivism, doesn’t mention it.
The problem I have with the whole question is the dissonance between grammatical form and actual content. With an exclusive focus on grammar, the rhetorical strategy behind this construction, so similar to a standard third conditional, is ignored: the unless protasis, though half of a speculative or hypothetical proposition, is not actually contrafactual, but assumed true, thus affirming strongly the opposite of the apodosis, which is really the whole point of the utterance. In this construction, unless dons the guise of being contrary to fact, while the rhetorical strategy of the construction is just the opposite. It’s not the naked waiter with the seaweed salad, but it is Moses having “it in him.”
We should not have asserted in our last number that Benefit Societies were very ill calculated to secure the comfort and independence of the workman, unless we had had something better to offer to their notice. — The Co-operator No. 13, 1 May 1829.
The unless clause is assumed to be true, thus the editors indeed asserted the disadvantages of benefit societies. The apodosis is false, but the point is its unspoken affirmative twin. Other examples follow the same pattern: an apodosis cast as a negative of a current state of affairs is proven false by an unless clause whose assumed truth is essential to the sentence.
Hesiod would not have recorded this relationship, unless he had believed, probably in the seventh century, that the Macedones were a Greek speaking people. — Nicholas G. L. Hammond, The Macedonian State, 1989.
But we must never forget that we would not have made the progress toward lasting peace that we have made in this past year unless we had had the military strength that commanded respect. — Richard Nixon, “Address to the Nation About Vietnam and Domestic Problems,” 29 Mar. 1973.
I am quite satisfied that the defendant would not have told Mr. Appelby about the rumour unless he had obtained his information from some source which he considered to be reliable. — Ngope v. O’Brien Quinn, 1987, Botswana e-Laws [broken link].
”I was so lonely — you know, you must have read that story I wrote; you couldn’t have painted that picture unless you had, and unless you had understood.” — Agatha Christie, “The Lonely God,” first pub. Royal Magazine, London, 1926.
“I believe Semyonov was not a merchant navy deckhand, but a courier. That conclusion seems to me unavoidable. I do not believe he would have gone to those lengths to protect what he was carrying, or to end his life to avoid what he must have thought would be interrogation by us, unless he had been instructed his mission was of crucial importance.” — Frederick Forsyth, The Fourth Protocol, Part 3, ch. 16, 1984.
It is not surprising that writers such as Frederick Forsyth and Agatha Christie using this construction — Fujita adduces an example from another work — beacause for them, it is less rhetoric than deductive reasoning, in these last two sentences beginning with a positive statement about a current state, then speculating how one got there.
The limitations on unless in closed conditionals is inherent in the meaning and semantic function of the word: a binary structure where only one, but not both propositions in a conditional sentence may be contrary to fact. This means statistically, unless will occur more frequently in open conditionals and “less freely” in closed ones.