SUMMARY: In traditional metaphysics a congenital confusion exists between «contingent» being and «possibile» being, two terms which seem to be identical. In the teaching of N. Hartmann, who is essentially a thinker of «modes», one finds his theory on the mode of con­tingency. In the comprehension of the mode of Hatmann's «contingency», there exists a «re-sidual» moment within his system, which is of a difficult solution. In actual fact, «contin-gency» can well exist not only in an «Aufheben» but also in a fundamental «Fehlen». Howe­ver, it will be a «Fehlen», postulated in its own sphere and understood within this sphere. This does not mean that it is not rooted within the basis of an ontological «discontinuous» being. To the solution of this problem, Duns Scotus made a valid contribution, by his dintin-ction of the «contingent» and the «possible», which can be understood as a mode very close to that of Hartmann. But Duns Scotus adds something more: the contingent is strictly related to the mode of acting rooted in the free will. An exact conception of acting through the free­dom of the will (wich is not found in any «intellectualistic» system, including that of Hart­mann) can help us to understand satisfactorily the intelligible residual moment of the contin-geny proposed by N. Hartmann.