[cap-talk] Authority vs. Information Flow

[Toby Murray]

Hi all on cap-talk,

I've got a question whose answer seems subjective that I'd like to put
forward to see whether there is a consensus one way or the other here.

The question involves whether there is a distinction between information
flow and authority. The question is "If Alice has authority over Bob,
does it follow that there exists an information flow from Alice to Bob?"

I've always presumed that the answer to this question was a definite
"yes". However, lately I'm not so sure.

Consider the following examples, which help to illuminate the nature o
the question.

Example 1: In which Authority and Information Flow Both Seem to Exist
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Bob sits in a room into which no sound, nor light can enter. There is a
light on the wall.

Alice is outside of the room and is given a button. When she presses the
button, the light in the room goes on.

Hence, Alice can cause Bob to be able to see the light turning on.

It seems straightforward to argue that Alice can pass information to
Bob.

Example 2: In which Authority exists, but perhaps not Info Flow
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Now imagine the same scenario, except that now there is a third party,
Dave. Dave also has a button like Alice, that turns on the light in
Bob's room when it is pressed. Both Alice and Dave now have control over
the light.

We presume further, that Bob's behaviour is fully specified and does not
permit the possibility that Bob will refuse to push his button if Alice
hasn't already pushed hers. We make a symmetric assumption for Alice.
Whoever pushes their button first, then, causes the light to turn on. 

Both Alice and Dave now have authority to cause Bob to be able to see
the light turn on. But can either of them pass information to Bob?

This question seems tricky because when Bob sees the light turn on, he
can't know for sure who turned it on (Alice or Dave). Hence, it seems
possible to argue that neither can pass information to Bob.

I'd be curious to know whether people believe that in this second
example, we should consider there to be an information flow from Alice
to Bob (equivalently from Dave to Bob) or not.

In order for Bob to be able to receive information from some party,
Alice, I wonder whether we require not only that
 (1) Alice can affect Bob in some way, but also that
 (2) in all other circumstances in which Bob behaves identically as to
when Alice can affect him as in (1), that when Alice doesn't act, Bob
isn't so affected. 

(1) says that Alice has authority over Bob in some way.
(2) says that when Alice wields this authority to cause some effect on
Bob, Bob can reason that she *must* have acted in order to cause the
effect. 

Cheers

Toby