Medieval religious rationalities. A Weberian analysis. By D. L. D'Avray. Pp. x+198. Cambridge: Cambridge University Press, 2010. £50 (cloth), £17.99 (paper). 978 0 521 76707 1; 978 0 521 18682 7Rationalities in history. A Weberian essay in comparison. By D. L. D'Avray. Pp. x+214. Cambridge: Cambridge University Press, 2010. £50 (cloth), £17.99 (paper). 978 0 521 19920 9; 978 0 521 12808 7