The purpose of this book is to give a sound economic foundation of
finance. Finance is a coherent branch of applied economics that is
designed to understand financial markets in order to give advice for
practical financial decisions. This book argues that for a sound
economic foundation of finance the famous general equilibrium model
which in its modern form emphasizes the incompleteness of financial
markets is well suited. The aim of the book is to demonstrate that
financial markets can be meaningfully embedded into a more general
system of markets including, for example, commodity markets. The
interaction of these markets can be described via the well known notion
of a competitive equilibrium. We argue that for a sound foundation this
competitive equilibrium should be unique. In a first step we demonstrate
that this essential goal cannot of be achieved based only on the
rationality principle, i. e. on the assumption utility maximization of
some utility function subject to the budget constraint. In particular we
show that this important lack of structure is disturbing as well for the
case of mean-variance utility functions which are the basis of the
Capital Asset Pricing Model, one of the cornerstones of finance. The
final goal of our book is to give reasonable restrictions on the agents'
utility functions which lead to a well determined financial markets
model.