This chapter examines how shifting and often contradictory definitions of atheism served as a conceptual lens through which early modern European thinkers interpreted Chinese thought (and many ‘others’). From the late sixteenth to the eighteenth centuries, representations of China moved through three major paradigms: the Jesuit inclusive model of ‘prisca theologia’, the French Enlightenment engagement with Oriental Spinozism, and the Lutheran-inspired German eclectic dismissal of Chinese philosophy as irrational. These framings did not simply reflect theological disputes but constituted an epistemic and political effort to classify, rank, and domesticate non-European traditions within a universalist historical schema. We argue that the category of atheism initially functioned as a marker of religious deficiency or subversion, but as European rationalism progressed, it was gradually replaced by the broader and more durable label of irrationality or weak rationality. This shift illustrates the (pre)colonial logic embedded in philosophical universalism, and its long-lasting influence on both academic and political narratives about non-Western traditions.