This is something that I've recently had someone tell me is not grammatically correct. Now, to be honest, it's not something I would likely ever use in everyday language but that doesn't necessarily mean it's not perfectly acceptable.

So, as an example:

That that you have eaten is poisonous.

This is similar (in my mind) to "That which...".

There are certainly examples of this both in modern usage (if you want to call it that), in the form of a Wikipedia article about ambiguity in a phrase that is missing punctuation:

That that is is that that is not is not is that it it is

According to this article's text, this phrase is grammatically acceptable:

The sequence can be understood as any of three grammatically-correct sequences, each with at least three discrete sentences, by adding punctuation:

  • That that is, is. That that is not, is not. Is that it? It is.
  • That that is, is that that is. Not is not. Is that it? It is.
  • That that is, is that that is not. Is not "is that" it? It is.

But, Wikipedia is not always trustworthy.

This also appears historically, possibly the most noteworthy appearance is in Shakespeare's Twelfth Night and Hamlet, though the latter may not be the same usage.

Twelfth Night, Act 4 Scene 2:

Bonos dies, Sir Toby: for, as the old hermit of
Prague, that never saw pen and ink, very wittily
said to a niece of King Gorboduc, 'That that is is;'
so I, being Master Parson, am Master Parson; for,
what is 'that' but 'that,' and 'is' but 'is'?

This is the fool, speaking in jest, though... one might suppose that poor grammar is used intentionally?

Hamlet, Act 5 Scene 1:

Imperious Caesar, dead and turn'd to clay,
Might stop a hole to keep the wind away:
O, that that earth, which kept the world in awe,
Should patch a wall to expel the winter flaw!
But soft! but soft! aside: here comes the king.

Here, I could see this as being a stand-alone sentence (That that earth should patch a wall...), so it may be applicable here... but I think the first "that" is not a pronoun here, so it may not be the same.

So, is there an explanation of this form? Is it acceptable? As you may expect, this is difficult to look up because there certainly are acceptable forms of "that that" that appear internally in sentences. This is not what I'm interested in.

  • 1
    Related, possible duplicate: english.stackexchange.com/questions/3418/…
    – user66974
    Mar 28, 2017 at 21:16
  • 2
    @Catija The two are inextricably connected—you can't separate them like that. Ungrammaticality is nothing but clumsiness or awkwardness to a not-precisely-definable-but-more-than-just-clumsy degree. To me, ‘that that’ in the sense ‘that which’ is on the ungrammatical side of the line, but it's not far from the merely clumsy side. To others (like you, it would seem) it is sure to fall on the opposite side of the line. I think we can both agree that it's not nearly as ungrammatical as “*That the you have eaten is poisonous” would be, for example. Mar 28, 2017 at 21:27
  • 1
    It is acceptable, if a bit silly.
    – Ricky
    Mar 28, 2017 at 21:39
  • 1
    @developerwjk - Yes, in "That that is true is absurd", the first 'that' is a cataphoric pronoun for 'that is true', and the second 'that' is an anaphoric pronoun for some statement of dubious truth. In "That that you ate is poisonous", the first 'that' is a [demonstrative] pronoun for what was eaten, and the second 'that' is a relative pronoun. Since the relative pronoun traces to another pronoun (the first 'that'), it can hardly be restrictive; and so modern English would use 'which' instead, and commas wouldn't hurt either.
    – AmI
    Mar 28, 2017 at 23:14
  • 3
    Do you just care about the sequence of words "That that," or are you talking about the specific grammatical structure used in "That that you have eaten is poisonous"? I'm not talking about sentences that only mention the word "that ("like "that that is the second word of your sentence") because I find those silly. I mean, there are also examples like "That that key unlocks this door is a fact" where "that that" is not interchangeable with "that which."
    – herisson
    Apr 21, 2017 at 18:09

3 Answers 3


It seems like this has been established in the comments, but in the interest of providing an answer, there's nothing ungrammatical about starting a sentence this way.

It's common to start a sentence with a pronoun and a determiner, as in this Confucius quote:

He who has really set his mind on virtue will do no evil.

Grammatically speaking, this is a variation on the same thing. Many writers, out of a belief that repeating a word is improper or just unpleasant, seem to substitute "which" for "that" in these situations. Ralph Waldo Emerson did so in the following quote:

That which we persist in doing becomes easier to do

But by most contemporary prescriptive rules for choosing between "that" and "which," that should be used when the restrictive clause alters the meaning of the sentence. Emerson wasn't merely adding the clause about persistence as additional information:

That, which we persist in doing, becomes easier to do

Contemporarily and prescriptively speaking, a more strictly adhering phrase would be:

That that we persist in doing becomes easier to do.

Just like a contemporary writer would generally prefer

Something that we persist in doing becomes easier to do

rather than

Something which we persist in doing becomes easier to do

But few people will judge Emerson for his stylistic choice of writing "that which," especially in poetry.

Another alternative, if you're interested in avoiding "that-that," is to use "what." "What" by definition can mean the thing or things that.

What is, is.

What we persist in doing becomes easier to do.

As pointed out in the question, using "that that" isn't foreign to talented writers. It is just as grammatical as the alternatives, and in many cases would be an appropriate thing to write. But if you're more interested in style and less interested in adhering to rules, you can rephrase sentences like this, and you'll be in the company of great writers either way.

  • Thank you for your response. I am not interested in rephrasing. I'm strictly interested in whether it is grammatically acceptable or not as is. :)
    – Catija
    Apr 27, 2017 at 17:34
  • @Catija I thought I'd add as much context to my answer as possible, but my short answer, and the apparent consensus answer, is that yes it is generally acceptable as is, especially "grammatically." I can't say it's "commonly used," probably because writers choose to deliberately avoid the repetition (e.g. with "that which" or "what") Apr 27, 2017 at 17:37

Sometimes it is acceptable in some conditions like that of the first example.

However, in examples such as these:

That that pencil, looks great!

it is grammatically incorrect as it is a pencil unless you rephrase it like this:

That . . . that pencil, looks great!

because of the speaker in awe. However, don't push your luck too much especially during exams as the marker might mark you down.


THEY SAID: "But by most prescriptive rules for choosing between "that" and "which," that should be used when the restrictive clause alters the meaning of the sentence. Emerson wasn't merely adding the clause about persistence as additional information:

'That, which we persist in doing, becomes easier to do'"

I SAY: I believe the sentence instead drops a word or phrase, and it was meant to be read as if it said "That [activity] which we persist in doing..."

Also, personally, it annoys me to no end when people use 'that that' or 'had had' -- because it is redundant and only the most bookish and grammarly people would understand different parts of speech.

There are better ways to phrase a sentence. To the original question, I believe sentences would be better with something like these:

"That it is true..." and "O, that the earth..."

In today's America, at least, we can barely get people to use the correct there/their/they're and stop using frigging apostrophes in every word that ends with an 's'. Making sentences like "That that is, is" -- simply IS beyond too many people now.

  • Really not sure what you're saying here. Sorry. I'm not asking for personal preferences. And SE doesn't really care what preferences are. I'm asking for sourced information that explains the validity or invalidity of this construction. I'm also not interested in "better" ways of writing it.
    – Catija
    May 1, 2017 at 21:37
  • Josh's reference english.stackexchange.com/questions/3418/… includes a great quote from A. Lincoln and an concise explanation of the three uses of "that." Really, the summation is easy; it's acceptable; it may be distracting and thus worthy of a rewrite.
    – Xanne
    May 1, 2017 at 21:58

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