"...probably knew the answer judging by..." Is this grammatically correct?

Question

Example:

"What do you think about my house?" Tommy asked, who probably knew the answer judging by my open mouth.

...who probably knew the answer judging by... has only one Google result. So I wonder whether it's grammatical.

Answer 1

Here's a simple example of a non-defining relative clause similar to OP's construction...

My sister, who lives in France, is coming to stay with me next week.
'who lives in France' is not essential, which means that I only have one sister and she does not need to be defined by the relative clause

In OP's case, there's only one Tommy - the extra information contained in the who clause simply tells us more about him, not which Tommy he is. In such constructions, the actual noun being referenced (Tommy, in this case) must immediately precede who...

"What do you think about my house?" asked Tommy, who probably knew the answer judging by my open mouth.

Other than the erroneous transposition of those two words, syntactically OP's text is perfectly normal English. It could be punctuated differently - for example, with a dash instead of a comma, or by placing the relative clause in brackets. But these are just stylistic choices.

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Having said that, although grammatically the example is fine after that minor change, it's semantically problematic once we stop to ask Who is actually doing this "judging"?. I'm afraid there's no obvious way to fix that - sometimes valid syntax lets you say things that are effectively nonsense.

Answer 2

This is not correct. 'Judging by ...' functions here as a comment phrase. In your sentence it means something like 'if one were to judge by my (open) mouth', which is not possible. . Thus we could say "Tommy knew how I felt, judging by the expression on his face". One possibility for what you want to say is "What do you think about my house?" Tommy asked, who probably knew the answer when he saw my jaw drop.

Answer 3

In this context, he is "judging" your answer from your body language.

Or more simplistically, he is guessing your answer from your body language, before you answer verbally.

You walk into his very nice house and your mouth drops open in astonishment. He sees this and knows you're impressed, he has already worked this out from your body language (your open mouth) but he asks you anyway, presumably because he's enjoying your reaction and wants you to praise his house.

Answer 4

On the surface it would seem grammatical and idiomatic to most native speakers. But when they looked more closely at that sentence, they would realize that it is not quite idiomatic. I suspect some may disagree with me on this.

"...judging by my open mouth" is the problemmatic phrase. It is not used as one would typically use it.

Here are some examples of proper uses:

Judging by your wet shoes, I assume you've been walking through puddles.

I assume you've been picking raspberries, judging by all those scratches on your hands and forearms.

To judge from the look on his face, he had just seen a ghost.

Here is an example of a non-idiomatic use:

"Have you been walking through puddles?" Tommy asked, who probably knew the answer judging by my wet shoes.

Why is that not idiomatic? The adverbial phrase "judging by {something}", when used idiomatically, refers to a judgment that is being made by the speaker of the sentence.

So what that sentence about Tommy actually says is this:

Judging by my wet shoes, I believe Tommy already knew the answer to his question, "Have you been walking through puddles?"

That is, the adverbial phrase modifies "I believe". It is a condition of that belief.

Here is that sentence corrected:

Judging from the way he had stared at my shoes, Tommy already knew the answer to his question, "Have you been walking through puddles?"

Answer 5

"What do you think about my house?" Tommy asked, who probably knew the answer judging by my open mouth.

The word "probably" plus the first person perspective (use of the word my) is causing a problem. By using these devices, you are speaking from a biased first person viewpoint - someone who is evaluating the probability that Tommy already knew the answer. Together, it seems to imply that the biased speaker is "judging by my open mouth", which is contradictory, though I'm sure an English speaker could figure out due to the contradiction that you in fact meant that Tommy is doing the judging.

If you want to keep the the biased first person perspective, I suggest trying to make who's doing what more clear:

"What do you think about my house?" Tommy asked, who probably knew the answer since my mouth was hanging open.