This multi-part series is about the nature of reality. One philosophy to consider is materialism, which is the guess that reality is not made of information at its core but is made of material or matter. The digital physics revolution is the increasingly popular belief among physicists that materialism is a false philosophy and that reality is literally made of information. If reality is made of information, two candidates for what its substrate would be include: (1) An emergent universal computer. Or (2) an emergent universal mind. Either one could serve as the substrate to hold and process information.