When Kant separated off the Critique of Practical Reason from the Critique of Pure Reason, he did not solely isolate ethics from the rest of philosophy, he also drained theoretical philosophy of any practical element, anything involving reason's capacity to change and improve reality (including, I will argue, itself). What theoretical philosophy lost with the splitting of the first and second Critiques was any claim to normativity, to rules and so to an epistemic 'ought'. I contend, however, that in eighteenth-century German philosophy Kant is the exception, not the norm. Both before him (in the Leibniz-Wolffian tradition) and after him (in Schiller and Maimon's work), epistemology is understood as thoroughly normative. Here reason is neither merely pure, nor merely practical, not even pure practicalit forms, instead, 'purely practical reason' which applies normative rules in every domain. In this paper, therefore, I argue for the centrality of normative ruleswhat I dub, philosophy's ameliorative vocationto both pre-and post-Kantian German epistemology. Philosophers such as Wolff, Mendelssohn, Schiller and Maimon understood themselves as changing the world, not merely understanding it: praxis, not contemplation, was their ideal (even in epistemology). This was an ameliorative philosophy that sets rules for the improvement of both itself and other forms of thought. My argument proceeds in three steps. First, I focus on one element of the Leibniz-Wolffian projectits attempt to eliminate symbolic cognitionin order to substantiate my thesis. There is a pressing need for research on Leibniz-Wolffian thought: the more ingrained a philosophical prejudice, the more urgently it calls for reappraisal, and there is no prejudice in the history of philosophy stronger than that against the Leibniz-Wolffian tradition of German rationalism. A dearth of studies, of translations and of basic conceptual familiarity with this period strongly suggests a need to attend to it. 1 It is, of course, Kant's three critiques which provide the justification for contemporary ignorance: we are too quick to accept that the transcendental turn inaugurated a radical sea-change in philosophical thought and so consigned eighteenth-century rationalism to oblivion. However, central to my argumentand this is its second stepis that the Leibniz-Wolffian conception of the theoretical philosopher as a prescriber of rules does not become obsolete with the onset of transcendental thought; it lives onin transfigured formin strands of post-Kantian philosophy. Schiller and Maimon, for example, still conceive of philosophy as an ameliorative enterprise. Even though the ameliorative self-understanding of the philosopher was particularly prominent in the Leibniz-Wolffian tradition, it lived on after the transcendental turn. In this respect at least, Kant's Copernican revolution did not bring about an immediate paradigm shift; for his successors, this aspect of the Leibniz-Wolffian tradition was neither obsolete nor antiquated. Finally, the third step of my argumen...