Probably no one has pushed for the mathematization of historical Jesus studies more than mythicist Richard Carrier.

When it comes to mathematizing history, we see such diverse ends of the spectrum such as Carrier and William Lane Craig using Bayes theorem (math) to, oppositely, “prove” there is only a 1/3 chance Jesus existed in Carrier’s case, or that the resurrection happened for Craig.  But this rigid quantifying of history may be missing the qualifying component, which we can see in analogous cases.  For instance, when assessing a body of data/evidence to evaluate it and assign a numerical value for whatever purpose (eg, a percentile grade for a portfolio of student writing), the underlying assessment/evaluation criteria are always quantitative and qualitative.  So, if I give an overall grade of 75% on word choice in a collection/portfolio of grade 6 student narrative writing, I mean the student consistently (quantifier) and effectively (qualifier) employed 5 senses and emotion words in his/her writing to create a picture in the mind of the reader.

We don’t normally realize the qualitative piece in assigning numerical probability because we have been operating under the same assumptions for so long that they are simply part of the background of our approach to the world.  But, in fact, such assumptions are there.  If you give a third-grade child a sheet of event pictures like cartoons of doing homework tonight or the sun rising tomorrow and ask them to assign probabilities, their answers will all over the place: eg., of course the sun will rise, it always has; what if the sun explodes; just because something happened in the past doesn’t mean it will in the future – and innumerable other judgment contexts. 

This also applies to probabilities, which are what historians are interested in (Caesar “likely” crossed the Rubicon).  As Nietzsche pointed out, while the probability of flipping a coin as heads is ½, this has no predictive authority because if I flip a coin 3 times and each time it comes up heads, there is no reason the assume the next flip will be tails, because the fourth flip is causally unaffected by the previous ones.  Each flip is a unique event unto itself.  The probability matrix is not a feature of the world, but a mathematizing projection.  And science does this everywhere.  Heidegger points out, for instance,

• Galileo projected that the motion of each body is uniform and rectilinear if every obstacle remains excluded, but also changes uniformly when an equal force acts upon it.  These are not discoveries of science but contexts within which beings of nature are interrogated.  Nature must be projected.  It is only in light of the mathematical opening and projection of nature, i.e., by delimiting [nature] through such basic concepts as body, motion, velocity, place, and time, that certain facts of nature become accessible as facts of nature. It is only on the basis of disclosing the mathematical constitution of nature that the knowing determination of nature obtains meaning and justification according to measure, number, and weight.  What was crucial and consequential about the achievements of Galileo and Kepler was not observation of facts and experimentation, since ancient science did this too, but the insight that there is no such thing as pure facts and that facts can only be grasped and experimented with when the realm of nature as such is circumscribed.  Thus, underlying all natural sciences from the beginning are propositions and cognitions, like, e.g., the principle of the permanence of substance: “In all change of appearances substance is permanent; its quantum in nature is neither increased nor diminished.”  Moreover, the principle of causality: “All alterations take place in conformity with the law of the connection of cause and effect.”   These propositions state something a priori about nature. More exactly put, these propositions state what belongs to nature as nature. These propositions contain a knowledge of what nature is, while at the same time this knowledge is not grounded in experience.  The greatness and superiority of natural science in the sixteenth and seventeenth centuries are based upon the fact that the investigators were all philosophers; they understood that there are no mere facts, but that a fact is what it is only in light of the explanatory concept and always in accordance with the range of such explanation (Heidegger, Analysis of Kant)

So, returning to probability, the point is that that if we toss a coin 100 000 time the results will basically be evenly distributed between heads and tails is a projection in the above sense, and tells us nothing about an event, eg, whether this next particular toss will result in heads or tails.  Science is about the object in general, not the thing in itself.  This is related to how Carrier’s cosmic sperm bank in Paul hypothesis can be quantified only after it is qualified, since Carrier qualifies it incorrectly and so his mathematical evaluation is wrong.

In this way, Carrier adopts some improbable interpretive choices, some of which, like the cosmic sperm bank hypothesis, are declared “crazy” even by other mythicists like Dr. Robert M Price: see time 54:04 ff of the video here: