Probabilities, determinism, true randomness, the Big Bang…
“We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Arabia. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of these stupefying odds it is you and I, in our ordinariness, that are here.”
That’s the opening paragraph of Unweaving the Rainbow, by Richard Dawkins. It is magnificent. But is it true?
We can distinguish two types of randomness:
- Randomness due to lack of knowledge: That’s when it’s impossible for us to know with perfect precision the multitude of factors, along with their multiple interactions, that will determine any given outcome. This doesn’t mean that the process itself is inherently random. It isn’t, it’s fully deterministic. It’s just that for all practical purposes it is random for us.
- Randomness as a fundamental property of nature: The phenomena observed in the world of quantum mechanics are thought to involve true randomness, that is, it’s not that they seem random to us because we lack full knowledge of all the factors involved or the computational power to build a predictive model if we knew them all; no, it’s a matter of real and fundamental randomness.
Discussing probabilities with respect to nature (nature in the broadest sense) can be confusing if it’s not clear what kind of randomness is being considered. Depending on the context, it may help to clarify whether one is discussing probabilities due to lack of perfect knowledge or probabilities in the quantum-mechanics sense. Sometimes things can get a bit muddled, or so it seems to me, when one begins to ponder the probabilistic aspects of reality in relation to natural phenomena outside of the uncanny realm of quantum mechanics.
Presumably, the laws of physics must be what they are, or at least they must be what they are in our universe since it began. Given the initial conditions of the Big Bang, what has happened ever since must have happened. Presumably even the initial conditions of the Big Bang could not have been different, as they themselves must have been the result of physics laws, laws that may forever be beyond the scope of our observation and understanding, but that must have been there nonetheless, unless we want to entertain the (fantastic) possibility that the creation of our universe was a spontaneous out-of-nothing event not preceded by anything at all.
If so, to what extent does it make sense to say that we are here “in the teeth of stupefying odds”? Even if humans were the only intelligent life form in the whole universe, nay, in the multiverse, we can’t say that we’re here by sheer luck. Our existence was embedded in the laws of physics. We had to exist.
And, most amazingly, you and I had to exist. No chance involved. It is from this perspective that I think it may not always quite make sense to talk about probabilities when talking about nature (again, outside of quantum mechanics). That’s often not the case, of course. In evolution, for example, we talk about random mutations and nonrandom selection, and it makes perfect sense. One can say that evolution has no necessary direction, and that there’s no reason to think that intelligence and self-awareness had to arise eventually. And this is, in a sense, true. Had the conditions on earth been slightly different, perhaps no species would have ever developed high intelligence. It’s useful to think about evolution as described, because it helps us to understand its mechanism. It’s similar to applying probabilistic reasoning to rolling dice. We have no better approach to understand and predict different outcomes. Even though the result of a given roll was already determined since the Big Bang, we can’t know it, and the best we can do is ascertain its likelihood from probabilistic thinking.
The point is just that we should at least keep in the back of our mind that, from the deeper perspective of the inexorable laws of physics, conditions on earth must have at all times been exactly what they were in the past, and what we observe in nature couldn’t have been otherwise.
All the above assumes hard determinism. Even the “true” randomness in evidence in quantum mechanics would need to be only apparent, as otherwise it would be acceptable to speak of luck in broader contexts.
Biologist Jerry Coyne gives an excellent example of what a non-deterministic view of nature would entail:
Again I assert that, at bottom, the evolution of chimps was “dictated” by the laws of physics: the deterministic forces as well as the random ones, which could include mutations. (I’ve argued that the evolution of life could not have been predicted, even with perfect knowledge, after the Big Bang, given that some evolutionary phenomena, like mutations, may have a quantum component.)
But even quantum mechanics does not necessarily prove that the universe is non-deterministic. For example, the many-world Interpretation* is compatible with a rigidly deterministic universe (or multiverse, rather). If this interpretation is correct, we have at least one scenario entirely compatible with hard determinism: Our existence, and I don’t mean humanity in general, but your existence and mine, and furthermore, what we’re doing this very instant, and what we’ll do every minute from now on, has been foreordained since the beginning of time, given that all the different quantum-mechanics-induced paths that our lives (and all preceding events) may have followed, have in fact been followed—just not in the same universe. Because every single possible outcome is actually taking place in one universe or another, randomness doesn’t play any role at all.
The notion of complete determinism can be disconcerting. Yet if nothing is truly random and you and I had to be here — if we are necessary components in an infinite equation, as it were — isn’t that fascinating?
*The fundamental idea of the Many-World-Interpretation is that there are myriads of worlds in the Universe in addition to the world we are aware of. In particular, every time a quantum experiment with different possible outcomes is performed, all outcomes are obtained, each in a different world, even if we are only aware of the world with the outcome we have seen. In fact, quantum experiments take place everywhere and very often, not just in physics laboratories: even the irregular blinking of an old fluorescent bulb is a quantum experiment. Source: The Stanford Encyclopedia of Philosophy.