How often have we heard, “It MUST HAVE been ..." or “something must have. ... This indeed is a special kind of conclusionary reasoning where we attempt to deduce causation backwards from the results – and go back in time with our deductions. We often do this as a matter of course without ever considering, nourishing nor dissecting the possibility that our conclusions may be unwarranted, foolish or off base.
We, for instance, tend to assume that nature requires a powerful cause to have a powerful effect. We tacitly assume a 1:1 relationship between cause and effect or between what we do not see versus what we do see. We hardly question the absurdity of such mental reasoning or conclusioning.
Consider one who sneezes and sets off an avalanche. Surely the sneeze may have been only 10 (a billionth) the power of the avalanche. But sometimes tiny events can have big effects. A mere “slip up” in DNA can cause a profound mutation. And we should never assume that each gene sponsors one trait, characteristic or behavior. One gene may cause 11 other events and perhaps 13 genes may control a particular kind of breast cancer. There is just no 1:1 relationship between genes and outcomes nor between events in history and after affects and ramifications. Consider a titration chemical experiment where some reagent is added to a liquid drop by drop and for 437 drops nothing seems to happen. Finally on the 438 drop, the liquid suddenly turns from clear to dark purple. But if we only witnessed the last drop we might have drawn a false conclusion about that causality.
In short, any time we observe any aftermath, we should be most careful about positing as to what we surmise lead up to and contributed to the site that we see. We cannot backtrack history in linear 1:1 fashion unless we enjoy being stupid and foolish. Indeed, “Must thinking makes us dumb. Also consider the difference between “may thinking” and “must thinking” as the difference between allowing a kite to fly and pulling a kite back down that is already flying. One is much easier and more obvious than the other. The degrees of freedom and range of possibilities is far fewer in pulling something down with a string although our imagination can hardly harness and subsume all realistic possibilities.