Arthur Collins's succinct, revisionist exposition of Kant's Critique of Pure Reason brings a new clarity to this notoriously difficult text. Until recently most readers, ascribing broadly Cartesian assumptions to Kant, have concluded that the Critique advances an idealist philosophy, because Kant calls it "transcendental idealism" and because the work abounds in apparent confirmations of that interpretation.

Collins maintains not only that this reading of Kant is false but also that it conceals Kant's real achievements. To counter it, he addresses the themes and passages in...