What Bolzano had to say about the Kantian conception of a priori knowledge in his early essay on the philosophy of mathematics, the Contributions to a Better Founded Exposition of Mathematics, is valuable on many accounts. In the Appendix to the latter — the title is On the Kantian Doctrine of the Construction of Concepts in Intuition — Bolzano criticises Kant's doctrine of pure intuition. The views he puts forward in the latter have been discussed in some detail (Laz 1993; Rusnock 2000; Sebestik 1992).¹ In fact, commentators tend to rely exclusively on this short text when it comes to assessing Bolzano's criticism of Kant's views on a priori knowledge. In 1810, however, Bolzano's theory remained overall tentative. In particular, Bolzano did not provide a substantial alternative to Kant's views. By contrast, in the Theory of Science, Bolzano not only offered a thorough and mature criticism that became the basis for the comprehensive assessment of Kant's philosophy later published under the title The New Anti-Kant (Příhonský 1850) but also developed his own alternative conception of a priori knowledge.