"The sharp polarisation of left and right is commonly dwelt on as the big political handicap of our times. Angry divisions on the right itself get less attention. Conservatism fills that gap. Across Europe and the US, a liberal right is at war with an illiberal right. As the leading force in politics, it is vital to understand the roots of the right's struggle with itself, how it stands and how it is likely to come out. From its early 19th-century...