The purpose of this book is to give a stream-lined introduction to the theory of Dirichlet forms on general state spaces. It includes both the analytic and probabilistic components of the theory. A substantial part of the book is designed for a one-year graduate course. It provides a framework which covers both the well-studied "classical" theory of regular Dirichlet forms on locally compact state spaces and all recent extensions to infinite-dimensional state spaces. It also contains a complete proof of an analytic characterization of the class of Dirichlet forms which are associated with right continuous strong Markov processes, i.e. those having a probabilistic counterpart. Finally, a general regularization method is developed which makes it possible to transfer all results known in the classical locally compact regular case to this (in the above sense) most general class of Dirichlet forms.
