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March 20, 2006

It's a Monty Hall universe, after all

Attention conservation notice: This mini-essay was written after one of my family members asked me what I thought of the idea of predestination. What follows is a rephrasing of my response, along with a few additional thoughts that connect this topic to evolutionary game theory.

Traditionally, the idea of predestination means that each person has a fixed path, or sequence of events, that constitute their life. From the popular perspective, this gets translated into "everything happens for a reason" - a statement that raises little red flags with me whenever someone states it earnestly. In my experience, this platitude mostly gets used to rationalize a notable coincidence (e.g., bumping into someone you know at the airport) or a particularly tragic event, and that people don't actually behave as if they believe it (more on this later).

I suspect that most people who find predestination appealing believe, at some level, in a supernatural force that has predetermined every little event in the world. But, when you get right down to it, there's nothing in our collective experience of the physical universe that supports either this idea or the existence of any supernatural force. But, there are aspects of the universe that are, in a sense, compatible with the idea of predestination. Similarly, there are aspects that are wholly incompatible, and I'll discuss both momentarily. The problem of course, is that these aspects are not the ones that a casual observer would focus on when considering predestination.

The aspect of the universe that is compatible with the idea of predestination comes from the fact that the universe is patterned. That is, there are rules (such as the laws of physics) that prescribe the consequences for each action. If the universe were totally unpredictable in every way possible, then there is no cause-and-effect, while a consistent and physically realistic universe requires that it exists. As a toy example, if you push a ball off a table, it then falls to the ground. To be precise, your push is the cause, the fall is the effect, and gravity is the natural mechanism by which cause leads to effect. If the universe were totally unpredictable, then that mechanism wouldn't exist, and the ball might just as well fly up to the ceiling, or whiz around your head in circles, as fall to the ground. So, the fact that cause-and-effect exists means that there's a sequence of consequences that naturally follow from any action, and this is a lot like predestination.

But, there's an aspect of the universe that is fundamentally incompatible with predestination: quantum physics. At the smallest scales, the idea of cause-and-effect becomes problematic, and the world decomposes into a fuzzy mass of unpredictability. There are still patterns there, but the strongest statements that can be made are only statistical in nature. That is, while individual events themselves totally unpredictable, when taken together in larger numbers, you observe that certain kinds of events are more likely than others; individual events themselves are random, while en mass they are not. Indeed, the utilization of this fact is what underlies the operation of virtually every electronic device.

Einstein struggled with the apparent conflict between the randomness of quantum theory and the regularity of the macroscopic world we human inhabit. This struggle was the source of his infamous complaint that God does not play dice with the universe. Partially because of his struggle, physicists have probed very deeply into the possibility that the randomness of the universe at the smallest level is just an illusion, and that there is some missing piece of the picture that would dispel the fog of randomness, returning us to the predictable world of Newton. But, these tests for "hidden variables" have always failed, and the probabilistic model of the universe, i.e., quantum physics, has been validated over, and over, and over. So, it appears that God really does play dice with the universe, at least at the very smallest level.

But, how does this connect with the kind of universe that we experience? Although the motions of the water molecules in the air around me are basically random, does that also mean that my entire life experience is also basically unpredictable? Well, yes, actually. In the 1960s, physicists discovered that large systems like the weather are "mathematically chaotic". This is the idea that very small disturbances in one place can be amplified, by natural processes, to become very large disturbances in another place. This idea was popularized by the idea that a butterfly can flap its wings in Brazil and cause a tornado in Texas. And, physicists have shown that indeed, the unpredictability of tiny atoms and electrons can and do cause unpredictability in large systems like the rhythm of your heart, the weather patterns all over the world and even the way water splashes out of a boiling pot.

So basically, predestination exists, but only in a statistical sense. Technically, this is what's called "probabilistic determinism", and it means that while hindsight is perfect (after all, the past has already happened, so it can only be one way), the future is unknown and is, at least until it happens, undetermined except in the statistical sense. Put another way, the broad brushstrokes of the future are predetermined (because the universe operates through natural and consistent forces), but the minute details are not (because the universe is fundamentally probabilistic in nature). If some supernatural force is at play in the universe and has predetermined certain features of the universe, then they are only very vague and general ones like life probably evolving on a planet somewhere (the "blind watchmaker" idea, basically), and not like the kind of events that most people consider when they think about predestination, such as attending a certain graduate school or falling in love with a certain person.

In summary, what I've tried to establish in the above paragraphs is that the belief in predestination is an irrational one because it's not actually supported by any physical evidence from the real world. But, the idea of predestination has a certain utility for intelligent beings who can only see a very small piece of the world around them. From any one person's perspective, the world is a very confusing and unpredictable place, and I think it's very comforting to believe that such an impression is false and that the world is actually very ordered beyond our horizon of knowledge. That is, holding this belief makes it easier to actually make a decision in one's own life, because it diminishes the fear that one's choice will result in really bad consequences, and it does this by asserting that whatever decision one makes, the outcome was already determined. So, it frees the decision-maker from the responsibility of the consequences, for better, or for worse. And, in a world where decisions must be made in a timely fashion, i.e., where one cannot spend hours, days, or years pondering which choice is best, which is to say in the world that we inhabit, that freedom from consequence is really useful.

In fact, this mental freedom is necessary for survival (although getting it via a belief in predestination is not the only way to acquire it). The alternative is a dead species - dead from a paralysis of indecision - which clearly has been selected against in our evolutionary history. But also, there are clear problems with having an extreme amount of such freedom. No decision making being can fully believe in the disconnect between their decisions and the subsequent consequences. Otherwise, that being would have no reason to think at all, and could make decisions essentially at random. So, there must then be a tension between the consequence-free and consequence-centric modes of decision making, and indeed, we see exactly this tension in humans today. Or rather, humans seem to apply both modes of decision making depending on the situation, with consequence-free thinking perhaps applied retrospectively more often than prospectively. Ultimately, the trick is to become conscious of these modes and to learn how to apply them toward the end goal of making better decisions, i.e., determining the relative gain in the quality of the decision against the extra time it took to come upon it. Of course, humans are notoriously bad judges of the quality of their decisions (e.g., here and here), so spending a little extra time to consider your choices may be a reasonable way to insure that you're happy with whatever choice you end up making.

posted March 20, 2006 05:43 PM in Thinking Aloud | permalink


Hi, this is actually a very interesting post. I've been mainly for predestination only because I couldn't think of any examples that would go against it, however I didn't know much about quantum mechanics as well. Thanks for connecting the two for us!

Posted by: Paul at March 21, 2006 06:11 AM