Over the past 40 years, Jim Cummins has proposed a number of highly influential theoretical concepts, including the threshold and interdependence hypotheses and the distinction between conversational fluency and academic language proficiency. In this book, he provides a personal account of how these ideas developed and he examines the credibility of critiques they have generated, using the criteria of empirical adequacy, logical coherence, and consequential validity. These criteria of theoretical legitimacy are also applied to the evaluation of two different versions of translanguaging theory – Unitary Translanguaging Theory and Crosslinguistic Translanguaging Theory – in a way that significantly clarifies this controversial concept. 

Jim Cummins is Professor Emeritus at the University of Toronto, Canada and has spent the past 40 years researching and working with multilingual learners across the world. His controversial theoretical distinction between conversational versus academic language proficiency is a key topic in pre-service and professional development related to the education of multilingual students who are learning the language of instruction.