First published in 1840, this two-volume treatise by Cambridge polymath William Whewell (1794-1886) remains significant in the philosophy of science. The work was intended as the ‘moral’ to his three-volume History of the Inductive Sciences (1837), which is also reissued in this series. Building on philosophical foundations laid by Immanuel Kant and Francis Bacon, Whewell opens with the aphorism ‘Man is the Interpreter of Nature, Science the right interpretation’. Volume 1 contains the majority of Whewell’s section on ‘ideas’, in which he investigates the philosophy underlying a range of different disciplines, including pure, classificatory and mechanical sciences. Whewell’s work upholds throughout his belief that the mind was active and not merely a passive receiver of knowledge from the world. A key text in Victorian epistemological debates, notably challenged by John Stuart Mill and his System of Logic, Whewell’s treatise merits continued study and discussion in the present day.