Wednesday, August 1, 2012

Tautologously equivalent intentions

Poirot intends that:

  1. either Samuel is not murdered by Martha or if Samuel is murdered by Martha, Martha is executed.
To that end, he asks the police to watch where Samuel is sleeping.

Notice that (1) is tautologously equivalent to:

  1. either Samuel is not murdered by Martha or Martha is executed.
But (2) is a very different intention from (1). For instance, (2) describes the following situation. Jake really hates Martha. Samuel makes Martha very miserable and Jake knows that Martha is considering murdering Samuel. Jake wants Martha either to fail in her intention—as then Samuel will make her miserable—or to be executed for murder. So he both encourages Martha to try to murder Samuel and asks the police to watch where Samuel is sleeping, so that either Martha fails in murder or she is executed. Jake's intention is very different from Poirot's, though tautologously equivalent to it.


James said...

But Jake doesn't merely intend (2). By your description, he also intends:

(2*) Martha is miserable or Martha is executed.

And surely it is for this intention, not (2), that we find his intentions bad.

Tom said...

Why can't (1) be said to be Jake's intention? Asking the police to watch Samuel while he sleeps is a means ill designed to result in Martha's execution for anything other than Samuel's murder.

Alexander R Pruss said...


I am not sure. It seems to be problematic to intend a disjunction with a problematic disjunct.


Well, if this is the only crime Martha is thinking of committing, it's not a bad means.

K Kell said...
This comment has been removed by the author.
K Kell said...

I am inclined to go beyond Quine that the content of the "that-clause" in propositional attitudes is not only opaque, but also sensitive to hyperintensionality. We may only substitute content that is either explicitly endorsed, or that follows some very few valid inferences inside the attitude. I'm not sure which I am willing to grant.

Jake believes that the Pythagorean theorem is true.

Jake believes that the 4 color map theorem is false.