Henry Sidgwick was already something of an enigma in Cambridge less than six years after his death, and recent interest in his work has tended to compound this by re-inventing him as a modern moral philosopher. The Moral Sciences Tripos that Sidgwick led as Knightbridge Professor from 1883 had been reshaped in 1860 by John Grote, the successor in the chair to William Whewell; and so to understand the Tripos as Sidgwick first encountered it in the 1860s we need to understand quite what Grote had in mind – and Grote himself is an important figure, having in 1862 composed a running critique of John Stuart Mill’s utilitarianism. Furthermore, until the foundation of the Economics Tripos in 1903 the teaching of political economy in Cambridge was directed almost entirely to the Moral Sciences Tripos. Alfred Marshall’s strenuous efforts to detach the teaching of economics from the Moral Sciences Tripos have tended to distort subsequent understanding of “Cambridge Economics” from Marshall, through Pigou, to Maynard Keynes. In any case, Marshall’s own economics developed from his studies of John Stuart Mill. In this lecture, Keith Tribe examines the nexus between utilitarianism, ethics and political economy, to the construction of which Mill, Grote and Sidgwick made important contributions.