There is a little debate going on in Puzzling StackExchange on this post: A river crossing puzzle

The issue is with this sentence:

Billie shouts: "They're also pretty small. I will only go with Devin alone."

Does Billie mean that he will only go if Devin is with him (as in he won't go alone), or does it mean that he will only go with Devin and but can also go alone?

I think it's the latter; Billie merely stated who he would and wouldn't go with, not whether or not he would go alone.

  • 3
    On the face of it, I’d interpret this to mean he will only go with Devin (so just the two of them together) He will not go by himself, with anyone other than Devin, or in any group with more than just himself and Devin.
    – Jim
    Commented Oct 24, 2020 at 23:04
  • 1
    I'd say it's part of the puzzle.
    – Hot Licks
    Commented Oct 24, 2020 at 23:33
  • 2
    Could also mean that Billie will not go in a group that includes Devin unless it is just the two of them.
    – nnnnnn
    Commented Oct 24, 2020 at 23:41
  • 2
    @nnnnnn - Or it could be that he'll only go in a group that leaves Devin alone.
    – Hot Licks
    Commented Oct 25, 2020 at 0:35
  • @HotLicks That's so funny! Commented Oct 25, 2020 at 0:36

1 Answer 1


The previous sentence, "[The boats are] also pretty small," serves as the justification when Billie says, "I will only go with Devin alone." Obviously, what Billie is saying is that the maximum number of people a boat can carry is limited. As a result, Billie needs to be selective with whom he chooses to go with, and so declares that he would only go with Devin. It also stands to reason that since Billie's preference is influenced by capacity concerns, he should not have any issue with going alone. There is nothing in the context of the problem suggesting that Billie would not move unless Devin is in the same boat with him, so it is logical to assume that your latter interpretation is indeed correct.

In short, for logic puzzles, we should not assume from more than what we are given. We are given that the boats are small - forcing Billie to limit the people he goes with - but we are not given any conditions that could justify Billie not being able to cross alone.


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