 A third question, discussed in detail by Guyer (1979 [1997: 264–273]) and Matherne (2019) is raised by Kant himself in §22: whether the common sense, understood as a principle or standard, is regulative or constitutive. This question, which Kant leaves unanswered, is especially puzzling because it appears from §21 that Kant already takes himself to have established that the common sense is a condition of the universal communicability of cognition.