Abstract In Reformed lands within seventeenth-century Europe, universities were granted the ‘liberty to philosophise.’ Yet what did this mean in practice? In the first part of this paper, the notion of ‘orthodoxy’ will be outlined, and it will be explained how, according to Gisbertus Voetius, ‘Christian Freedom’ and the ‘ Libertas philosophandi ’ might go together. Orthodoxy, however, implied a clearly defined confession as well, circumscribing true faith. As a result, ‘academic freedom,’ though real in some ways, was necessarily limited. In the second part of this paper, the examples of Antonius Walaeus and Abraham Heidanus will show how both the new and the old philosophy might be presented as being consistent with orthodoxy in seventeenth-century Holland.