This special issue of Educational Studies in Mathematics, developed from the Mathematics Education and Contemporary Theory (MECT) conferences in Manchester, U.K., follows up an earlier double special issue in Volume 80 (2012) of this journal, which comprised 18 papers authored from a dozen countries. These efforts-both in conference and in print-to develop theory in and for mathematics education should be seen as part of our community's collective effort to offer mathematics education broader yet more rigorous Bthinking tools^. We argue in this introduction that in these times where ideology so often defines Bimprovement^in preference to rigorous analysis, this effort is more important than ever before. The selected papers span two broad areas: theory is used to develop critical conceptual frameworks for studies in mathematics education by Llewellyn, Nolan, Barwell, Nardi, Pais; and philosophical dimensions of mathematical learning are discussed by Ernest, Skovsmose, and Boylan.School mathematics is increasingly viewed as part of the armoury deployed in responding to political demands for economic and technological development. Schooling in general, and mathematics education in particular, is increasingly shaped, funded and judged by its perceived capacity to deliver success in terms of the prescribed quantitative measures by which so many governments reference their ambitions and achievements. Good performance here has sometimes been taken as being indicative of wider economic potential: the policy rhetoric suggests that the more we can improve in those areas the better for our future national well being.