This book describes Universal Plan (UP) theory. It says everything that exists is built from the same basic template of ideas. Claims include that it is the simplest most parsimonious explanation of existence conceivable, and is logically necessary. It is a complete theory of everything for a non-physical universe, generally compatible with philosophical idealism and simulation theory. UP theory is a new paradigm-shifting model of reality derived from first principles, with wide and profound implications. Science / AI: - A new theory of information and language. - The universe is made of information, it is a simulation. - A unification of human and computer languages, and all types of information. - A computational theory of mind and a new mapping of the senses. - Improved definitions for: logic, information, infinity, and many other concepts. - E.g. all paradox removed from the concept of infinity. Physics: - Everything is made of light. A unified "aether" model of physics. - New mechanical models of matter, charge, and magnetism. - A new theory of light and energy, entropy and order. - A new perspective on time, and on space / time. - A four-primary model of colour and colour vision. - The order of colours in the spectrum can be derived from logic. - An interference model of the prism. - The prism has never been properly understood. Philosophy - A definitive theory of categories (ontology). - A natural explanation and definition of morality. - Logical proof of "God", and an analysis of free will. - Rediscovery of "Alchemy" and the original "Philosopher's Stone".