This book suggests that applied linguistics research is inherently concerned with complexity, emergence and causality, and because of this it also requires a robust social ontology. The book identifies and unpacks a range of conceptual issues in applied linguistics from a social realist perspective, and provides a critique of successionism and interpretivism as two dominant and enduring empiricist tendencies in the field. From this critique, it considers the emergence of complex dynamic system theory as viable yet not entirely unproblematic conceptual sophistication of current applied...