This book is based on lectures I gave at the Department of Mathematics and
Statistics, University of Helsinki, during the academic year 2005–2006. I am
indebted to the students who followed the course, in particular to Åsa Hirvonen,
Meeri Kes¨al¨a, Ville Nurmi, Eero Raaste, and Ryan Siders. Thanks also go to
Ville Nurmi for suggesting numerous corrections to the text, compiling the
solutions to the exercises in the course, and for allowing me to include the
solutions in this book. I am very grateful to Wilfrid Hodges for many useful
discussions on dependence. I thank the Newton Institute (Cambridge, UK)
for inviting me for the five weeks, during which time the final manuscript
was prepared. The preparation of the manuscript was partially supported by
grant 40734 of the Academy of Finland. I wish to thank Peter Thompson of
Cambridge University Press for all the arrangements concerning publishing,
and I am deeply grateful to Juliette Kennedy for her generous help in all stages
of writing this book