I’d like ask about the sentence from The Naval Treaty by Conan Doyle.

“How are you, Watson?” said he, cordially. “I should never have known you under that moustache, and I daresay you would not be prepared to swear to me.

The speaker Phelps met Dr. Watson for the first time in many years in this moment. I can understand the first half of his remark, but what does “I daresay you would not be prepared to swear to me” part say? The first part is “Hello, I’ve never seen you with that moustache before.” or just “Oh, you’ve come to wear such moustache? I didn’t know that.” when you paraphrase this, right? So the last part has to mean like “And I think I should look unfamiliar to you since it’s been many years since we last met.” But does it say so, with this “I daresay ..” stuff? I don’t know. Can anyone paraphrase the last part for me or tell me what the object for the verb “swear” , if the verb is being used as a transitive verb here? Thanks.

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    No, it's "I wouldn't have recognised you now you have grown a moustache, and I dare say you wouldn't have been absolutely sure who I am" (if Watson hadn't known in advance who he was meeting). Jan 12, 2020 at 8:49
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    If you replace "me", with "who I was either" it may become clearer. The last part simply means "... and I daresay you wouldn't be prepared to swear to (who I was either)".
    – WS2
    Jan 12, 2020 at 9:10

1 Answer 1


This is an unusual use — or now an unusual use — of swear to:

swear to phrasal verb

  1. To affirm with an oath; to express assurance of the truth of (a statement), or the identity of (a person or thing), by swearing.

1908 R. Bᴀɢᴏᴛ Anthony Cuthbert xxiv. 315 You could swear to its authenticity, or the reverse, if necessary?


That is, just as swear to its authenticity means "to make an oath that it is authentic"; this use of swear to me means "make an oath that I am me."

It doesn't indicate that the speaker is administering an oath (as one might swear to a magistrate to do something).

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    The meaning of swear to is only one issue here. It also took me a few seconds to work out what was meant by "swear to me" - clearly "swear to who I was" is what the author is saying.
    – WS2
    Jan 12, 2020 at 10:29

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