My comment above strongly called into question whether CDT gives the right answers. Therefore I wouldn’t try to reinvent CDT with a different language. For instance, in the post I suggest that we should care about “all” the outcomes, not only the one happening in the future. I’ve first read about this idea in Paul Almond’s paper on decision theory. An excerpt that might be of interest:
Suppose the universe is deterministic, so that the state of the universe at any time
completely determines its state at some later time.
Suppose at the present time, just before time t_now, you have a choice to make. There is a
cup of coffee on a table in front of you and have to decide whether to drink it.
Before you decide, let us consider the state of the universe at some time, t_sooner, which is
earlier than the present. The state of the universe at t_sooner should have been one from
which your later decision, whatever it is going to be, can be determined: If you
eventually end up drinking the coffee at t_now, this should be implied by the universe at
t_sooner.
Assume we do not know whether you are going to drink the coffee. We do not know
whether the state of the universe at t_sooner was one that led to you drinking the coffee.
Suppose that there were a number of conceivable states of the universe at t_sooner, each
consistent with what you know in the present, which implied futures in which you drink
the coffee at tnow. Let us call these states D1,D2,D3,…Dn. Suppose also that there were a
number of conceivable states of the universe at t_sooner, each consistent with what you
know in the present, which implied futures in which you do not drink the coffee at t_now.
Let us call these states N1,N2,N3,…Nn.
Suppose that you just drunk the coffee at t_now. You would now know that the state of
the universe at t_sooner was one of the states D1,D2,D3,…Dn. Suppose now that you did not
drink the coffee at t_now. You would now know that the state of the universe at t_sooner was
one of the states N1,N2,N3,…Nn.
Consider now the situation in the present, just before t_now, when you are faced with
deciding whether to drink the coffee. If you choose to drink the coffee then at t_sooner the
universe will have been in one of the states D1, D2, D3,…Dn and if you choose not to drink
the coffee then at t_sooner the universe will have been in one of the states N1,N2,N3,…Nn.
From your perspective, your choice is determining the previous state of the universe, as
if backward causality were operating. From your perspective, when you are faced with
choosing whether or not to drink the coffee, you are able to choose whether you want
to live in a universe which was in one of the states D1,D2,D3,…Dn or one of the states
N1,N2,N3,…Nn in the past. Of course, there is no magical backward causality effect
operating here: The reality is that it is your decision which is being determined by the
earlier state of the universe. However, this does nothing to change how things appear
from your perspective.
Why is it that Newcomb’s paradox worries people so much, while the same issue arising
with everyday decisions does not seem to cause the same concern? The main reason is
probably that the issue is less obvious outside the scope of contrived situations like that
in Newcomb’s paradox. With the example I have been discussing here, you get to
choose the state of the universe in the past, but only in very general terms: You know
that you can choose to live in a universe that, in the past, was in one of the states
D1,D2,D3,…Dn, but you are not confronted with specific details about one of these states,
such as knowing that the universe had a specific state in which some money was placed
in a certain box (which is how the backward causality seems to operate in Newcomb’s
paradox). It may make it seem more like an abstract, philosophical issue than a real
problem. In reality, the lack of specific knowledge should not make us feel any better: In
both situations you seem to be choosing the past as well as the future.
You might say that you do not really get to choose the previous state of the universe,
because it was in fact your decision that was determined by the previous state, but you
could as well say the same about your decision to drink or not drink the coffee: You
could say that whether you drink the coffee was determined by some earlier state of the
universe, so you have only the appearance of a choice. When making choices we act as
if we can decide, and this issue of the past being apparently dependent on our choices is
no different from the normal consequences of our future being apparently dependent
on our choices, even though our choices are themselves dependent on other things: We
can act as if we choose it.
It goes the other way round. An excerpt of my post (section Newcomb’s Problem’s problem of free will):
Perceiving time without an inherent “arrow” is not new to scienceandphilosophy, but still, readers of this post will probably need a compelling reason why this view would be more goal-tracking. Considering the Newcomb’s Problem a reason can be given: Intuitively, the past seems much more “settled” to us than the future. But it seems to me that this notion is confounded as we often know more about the past than we know about the future. This could tempt us to project this disbalance of knowledge onto the universe such that we perceive the past as settled and unswayable in contrast to a shapeable future. However, such a conventional set of intuitions conflicts strongly with us picking only one box. These intuitions would tell us that we cannot affect the content of the box; it is already filled or empty since it has been prepared in the now inaccessible past.
I claim EDT is irrepairably broken on far less exotic problems than Parfit’s hitchhiker. Problems like “should I give drugs to patients based on the results of this observational study?”
This seems to be a matter of screening off. Once we don’t prescribe drugs because of evidential reasoning we don’t learn anything new about the health of the patient.
I would only not prescripe the drug if a credible instance with forecasting power (for instance Omega) shows to me that generally healthy patients (who show suspicious symptoms) go to doctors who endorse evidential reasoning and unhealthy patients go to conventional causal doctors. This sounds counterintuitive, but structurally it is equal to Newcomb’s Problem: The patient corresponds to the box, we know it already “has” a specific value, but we don’t know it yet. Choosing only box B (or not to give the drug) would be the option that is only compatible with the more desirable past where Omega has put the million into the box (or where the patient has been healthy all along).
My comment above strongly called into question whether CDT gives the right answers. Therefore I wouldn’t try to reinvent CDT with a different language. For instance, in the post I suggest that we should care about “all” the outcomes, not only the one happening in the future. I’ve first read about this idea in Paul Almond’s paper on decision theory. An excerpt that might be of interest:
This quote seems to be endorsing the Mind Projection Fallacy; learning about the past doesn’t seem to me to be the same thing as determining it...
It goes the other way round. An excerpt of my post (section Newcomb’s Problem’s problem of free will):
This seems to be a matter of screening off. Once we don’t prescribe drugs because of evidential reasoning we don’t learn anything new about the health of the patient. I would only not prescripe the drug if a credible instance with forecasting power (for instance Omega) shows to me that generally healthy patients (who show suspicious symptoms) go to doctors who endorse evidential reasoning and unhealthy patients go to conventional causal doctors. This sounds counterintuitive, but structurally it is equal to Newcomb’s Problem: The patient corresponds to the box, we know it already “has” a specific value, but we don’t know it yet. Choosing only box B (or not to give the drug) would be the option that is only compatible with the more desirable past where Omega has put the million into the box (or where the patient has been healthy all along).