As Tom Stoppard illustrated so well in his play, Arcadia, we humans have a desperate need for certainty in situations where, generally, there is none to be had. Psychologically, most of us feel rather uncomfortable maneuvering through life without rock solid narratives to explain the myriad things, both large and small, that matter to us. I know I have all sorts of explanations for all manner of human phenomena, but, I must say that, though I hew to a variety of views quite strongly, I always try to be aware that, to paraphrase Hamlet, there are more things on heaven and earth than are dreamt of in one's philosophy.
All this by way of saying that no matter how well one thinks one has thought something through, there are always things one has simply not accounted for. Now, of course, sometimes the probability that one has left some crucial aspect or two out of their brilliant formulation is low, but, even that, outside of the limited purview of very hard science, is a state of affairs that is, to to a greater or lesser extent, simply unknowable. At this point you may be, just perhaps, wondering what shaky (according to me) positions I have in mind when I prattle on about unknowability? All in good time.