This is of interest to me because, as I have already tried to emphasize, it is not that nature has ceased to be zuhanden in the broken tool or the airport delay. Whether we trip over a hidden tree stump, catch sun-glare on the windshield while driving to an appointment we are late for, snap a screw-driver in the midst of a last minute fix, or get attacked by a bear while trying to survey some wooded forest land, nature not only asserts itself and interferes, but it does so only within and through a world in terms of which, for example, we might disclose ourselves through panic, and our 'world' might go to pieces.
So the point is: the broken tool is not only a sign of the illuminating retraction of, but also the assertion of world. We would almost want to speak of two worlds passing by each other and intersecting on the way, were it not for the phenomenal evidence before us: the worlds are not so radically different as to not be understood as the singular world of In-der-Welt-Sein, and these retractions and assertions, it must at least be provisionally conceded, have as their common ontic site innerweltlich Seiendes. Thus the question is, how does one account for the paradoxical interference of φύσις in which world is at once asserted and rescinded? Again, one cannot say that this is reducible to the traditional distinction between nature and artifice for many reasons, but perhaps the obvious and most persistent one is the one we have already indicated: nature and artifice are not to be distinguished according to vor- and zu-handenheit. Nature is already zuhanden, but zuhandenheit is already natural --and yet not at all because there are natural things -- a collection of individual substances or 'objects' in the 'great outdoors'. The plane that you can't take to Boston might very well have frustrated your future and thus lit up the 'fact' that the world you are in also lies ahead of you, but it has done so just as much through a startling assertion of the world which I would now, imputing a different sense to the word, want to call a physiological assertion. However, the physiological assertion enacts itself just as much as it is already contained in the world, the same world capable of illuminating retraction: the sudden snowstorm not only disrupts, it also surprises.