After a year-long public battle with cancer, the writer and cultural critic Christopher Hitchens died this Thursday. Commenting on his early death, Hitchens reportedly told NPR that he was “dealt a pretty good hand by the cosmos, which doesn’t know I’m here and won’t know when I’m gone.” Hitchens made this comment because he was a fervid atheist. However, the statement could be valid even if the universe has a creator. It all depends on whether you think the universe is computable or not. (By all accounts, it is at least well approximated by a computable universe.) If the universe is computable, then in principle it is equivalent to one (or many) of the countably infinite number of possible computer programs. This implies that it is possible that someone wrote the program that generated our universe and this person would in fact be the Creator. However, depending on the cardinality of the Creator (by cardinality I mean the size of a set and not a reference to Catholicism), the Creator may or may not know that you or any thing at all exists in her universe.
Let’s take a specific example to make this more concrete. It has been shown that simple cellular automata (CA) like Rule 110 are universal computers. A CA is a discrete dynamical system on a grid where each grid point can be either 1 or 0 (i.e. bits) and there is an update rule where the bits stay the same or flip on the next time step depending on the current state of the bits. (Rule 110 is a one-dimensional CA where a bit is updated depending on the state of its two nearest neighbours and itself.) Thus every single possible computation can be generated by simply using every bit string as an initial state of Rule 110. So the entire history of our universe is encoded by a single string of binary digits together with the bits that encode Rule 110. Note that it doesn’t matter if our universe is quantum mechanical since any quantum mechanical system can be simulated on a classical computer. Thus, all the Creator needed to do was to write down some string of digits and let the CA run.
Now, what constitutes “you” and any macroscopic thing in the universe is a collection of bits. These bits need not be contiguous since nothing says that you have to be local at the level of the bits. Thus you would be one of all the possible subsets of the bits of a binary string. The set of all these subsets is called the power set. Since, any bit can either be in a subset or not, there are sets in the power set. Thus, you are one of an exponential number of possible bit combinations for a finite universe and if the universe is infinitely large then you are one of an uncountably infinite number of possible combinations. Hence, in order for the Creator to know you exist she has to a) know which subset corresponds to you and be able to find you and b) know when that subset will appear in the universe. Thanks to the brilliance of Georg Cantor and Alan Turing, we can prove that even if a Creator can solve a) (which is no easy task), she cannot solve b) unless she is more powerful than a classical computer. The reason is because in order to solve b), she has to predict when a given set of symbols will appear in the computation and this is equivalent to solving the Halting Problem (see here for a recent post I wrote introducing the concepts of computability). Hence, knowing if “you” will exist, is undecidable. In a completely self-consistent world where every being is computable, no being can systematically determine if another being exists in their own creation. In such a universe, Hitchens’s is right. However, the converse is also true so that if there is a universe where there is a Creator that knows about “you”, then that Creator must also be computationally more powerful than you.