Natural information processing systems such as biological evolution and human cognition organize information used to govern the activities of natural entities. When dealing with biologically secondary information, these systems can be specified by five common principles that we propose underlie natural information processing systems. The principles equate: (1) human long-term memory with a genome; (2) learning from other humans with biological reproduction; (3) problem solving through random generate and test with random mutation; (4) working memory when processing novel information with the epigenetic system managing environmental information; (5) long-term working memory with the epigenetic system managing genomic information. These five principles provide an integrated perspective for the nature of human learning and thought. They also have implications for the presentation of information.