I was watching an interesting panel discussion from the World Science Festival 2009 called Time Since Einstein that Sean Carroll, a participant in the discussion, pointed to. However, during the discussion (in segment 2 of 5), the moderator, who was not a physicist asked the following question:
If there is a future, physically speaking, do you believe that that means that it’s also determined and there’s kind of no point in doing one thing or the other, that it’s all been figured out? Can there be a non-deterministic future that exists independent of this flow of time?
The second question was the one that was answered, but the content of the first question is what interests me. The moderator seems to be indicating that if the future is determined, that there’s “no point in doing one thing or the other, that it’s all been figured out”, which betrays an erroneous concept of the relationship between determinism and choice.
Determinism is well summed up by Wikipedia as:
So essentially, in determinism, cause and effect invariably holds. If you had unlimited computational power and knew the universe’s past in every minute detail, you could extrapolate its future with certainty. Now, superficially, this may seem problematic for the concept of choice, especially when you consider that a deterministic future cannot be changed—it is fixed.
But this intuition is mistaken precisely because human intuition is not meant to apply to the viewpoint of an omniscient observer with unlimited computational power. We are very much ignorant of the world and limited in our ability to assess what we do know. At the very least this means that we should be wary of drawing quick conclusions when conceptualizing the world from the point of view of an omniscient observer.
But these limitations are very important to understanding choice. An omniscient actor in a deterministic universe in fact has no need for choice, as such an actor would know without deviation all of its future actions. Choice for us requires multiple steps that are irrelevant to the omniscient actor. The first and most important of these is the recognition of options.
In a given situation, there are usually multiple ways that we can conceive of acting. For instance, at a grocery store, one may choose between buying one of three brands of peanut butter. So, the shopper can recognize the options and then begin to weigh them.
One way of weighing the option is to create counterfactual scenarios. That is, imaging the results of choosing each option. This capacity probably is the reason that a fixed future intuitively seems to prohibit choice. After all, if only one future is possible, then you really can only choose one of the three options.
But it’s important to recognize that the imagined future is not real and is part of the process of making the choice. The notion that you, given your knowledge, preferences, and the dynamics of your decision-making process, would end up making a particular choice given a certain situation with no chance of making the other choices does not preclude the act of making a choice.
To look at it another way, the counterfactual scenarios—the future where you’ve picked up a container of JIF peanut butter, the future where you’ve picked up a container of Skippy peanut butter, and the future where you’ve picked up a container of the grocery store’s generic brand of peanut butter—are all projections based upon your own expectations and only exist within your mind. The future that actually occurs happens after you’ve made your choice.
In a deterministic universe, you will make a specific choice as a result of your preferences and decision-making process applied to the situation at hand and there’s no chance (from the view of the omniscient observer) that you would have made any other choice. But that doesn’t mean that replacing you with someone else given the same situation would necessarily provide the same result.
The problem with the notion that in a deterministic universe, there’s “no point in doing one thing or the other” is that your decision making process is an integral part of how things turn out, so accepting that viewpoint would (counterfactually) alter your decision making process and thus lead you to a different result than if you had chosen to reject that erroneous attitude toward the world.
It’s important to keep in mind that you approach the world from a human’s point of view and not from that of an omniscient observer. Intuitions that are useful in the world of humans can be misleading when trying to hypothetically explore the world through the eyes of the omniscient.