Book excerpt: This Book contains a new proposal for physics within more than four dimensions (3 spatial dimensions + 1 time coordinate). An extra space is introduced, called basic space, instead of extra dimensions, compactified or otherwise embedded in space-time. A "dual space concept" has been applied by the author to construct models of particles, photons and nuclei mainly in a bottom -- up process. The top - down reasoning, the dominating method in theoretical physics, is only used in a second step. The kind of "twofold existence" discussed in this book turns out to be useful for describing natural systems in the living and non-living world.