From Boston Legal (or your everyday conversation):

"He and I will be going on a little vacation."


"Probably best you don't know."

Being short for "It would probably be best if you didn't know," the spoken version changes the past tense to the present in the second half of the sentence.

Is this something a grammarian would find fault with? Or dismiss it as colloquial?

  • The long form could also use the present tense in the if-clause: "It would probably be best if you don't know." So I don't imagine that grammarians would find fault with the shortened version.
    – Shoe
    May 29 at 8:08
  • @Shoe: I beg to differ. I mean, shouldn't the presence of "would" automatically suggest the past tense?
    – Ricky
    May 29 at 8:10
  • 1
    "Would" in the main clause combined with past tense in the if-clause produces what is often called a second conditional. This is certainly a common pattern. But it is not a rule to be followed on all occasions. In conversational English it is natural and grammatical to mix up the tenses in the two clauses.
    – Shoe
    May 29 at 8:15
  • 2
    I'm not a grammarian, but I'd nit pick over the spelling of your title. :p
    – ralph.m
    May 29 at 9:45
  • 1
    "A grammarian", surely, but, to prevent closure based on matter of opinion, you might want to rephrase it to "is this sentence grammatical?" or something of the sort.
    – Joachim
    May 29 at 13:16

2 Answers 2


Nitpicking grammarians don’t tend to correct speech; in fact they probably talk just like you do. And if they don’t now, they will when the subjunctive altogether slips away from the language.

But since you asked . . .

Let’s say that it’s is elided in front of best. The expression it’s best, like it’s essential and it’s important, is followed by that (not if), and it triggers the “present” subjunctive (which uses the bare infinitive). Here the grammatical person is changed so you can better see it:

It’s essential [that] I be on time. (Not *It’s essential if I be on time.)
It’s essential [that] I not be late. (Not *It’s essential [that] I do not be late.)
It’s best [that] he know. (Not *It’s best if he know.)
It’s best [that] he not know. (Not *It’s best [that] he do not know.)

So: Best you not know. (Not *Best you don’t know.)

Let’s say that it would be is elided in front of best. Now we have an “unrealized” conditional (followed by if — not that), and it triggers the “past” subjunctive (which uses the past tense except with be in the first and third person singular):

It would be best if you didn’t know. (Not *It would be best if you don’t know.)
It would be best if he were unaware. (Not *It would be best if he was unaware.)

So: Best you didn’t know. (Not *Best you don’t know.)

Let’s say that it will be is elided in front of best. Now everything seems to be business as usual:

It will be best if you don’t know.

So: Best you don’t know.

  • I knew I could count on you.
    – Ricky
    May 30 at 2:54

No, a nitpicking grammarian would have no grounds to assume that the phrase did not stand for:

  • It is probably best you don't know.

Which is why we are quite likely to find reduced sentences such as:

  • Probably best that you don't know.

There are no nits here to be picked.

  • 1
    What's don't for here? Isn't it just best you not know?
    – tchrist
    May 29 at 12:33
  • 1
    @tchrist Depends on whether you want a tensed clause or a subjunctive one as the complement of know. Both are possible. Subjunctive clause more common in US English and tensed one in UK - but both occur in both varieties. May 29 at 12:41
  • @tchrist Oops I should have said “as the extraposed subject of be best not the complement of know. Apologies. May 29 at 18:44
  • @Araucaria-Nothereanymore. Interesting! It might be worth noting that the missing "It is" is a case of conversational deletion.
    – alphabet
    May 30 at 2:40

Not the answer you're looking for? Browse other questions tagged or ask your own question.