A common but very odd statement (about odds) was repeated on James McGrath's blog today. Quote: "Historians do not have access to H. G. Wells's time machine. We cannot know what occurred in the past and thus do not dogmatize about it. We deal only in probabilities." (Click for source.) In some quarters of Biblical Studies, this is an all too common assertion. It's also incredibly wrong.
First of all, for a position so set against dogma, it's third sentence itself is extremely dogmatic. "We deal only in probabilities." I reply, "Says who?" and "As if." In practice, historians deal in judgment, analysis and reconstruction. Probability is only one aspect of the judgment factor. A researcher collects evidence, determines whether that evidence is worthy to admit into her considerations, and then proceeds.
Probability does not exclusively govern the weighing of evidence.
Second of all, it is actually true that we *can* often know what occurred in the past. Relatively. (Because time is.. you know.) We know a lot about AD 2009, for example. We know less about 0009 BC, but we take what we're given and put details together the best that we can. True, many of those details will not be certain, and others will be, but no calculations can tell us that something did or did not happen, absolutely.
"Probability" doesn't do much to tell us whether Tiberius Caesar walked on foot through the Alps, leading his brother's body to Rome. It sounds incredible. It seems unlikely that someone would actually do that. Only Suetonius tells us this detail. Thus, probability suggests the claim may be untrue. Yet, it may just have happened.
Mathematically, "the more probable event" only occurs between 50 and 100 percent of the time. That leaves an awful lot of room left over for the less probable. The British defeat of the Spanish Armada seems unlikely, until you learn more of the facts. But we have so little data. So, then, we acknowledge the unknown unknowns. Something one might not have considered - or could not have calculated - can sometimes explain everything, reversing probability in its farthest extremes.
Fact: Historians cannot and do not restrict themselves "only" to what seems more probable.
For better and/or for worse, this game is far less scientific than some would have you believe.