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// Foreword 
// Story: Her Most Faithful Students 
// by Equimorto 
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Given a sufficiently large amount of tests, if all outcomes but one result the same it is perfectly acceptable to consider the outlier as nothing more than a fluke, something derived from outside interference, incorrect execution of the procedure or maybe a mistake during the measuring process. It is in fact encouraged to do so, as otherwise what is likely just the product of an error would alter the correct analysis of the experiment's results. Not to mention, given the fact that said anomalous outcome was derived from what was supposed to be a standard repetition of the same test, it's rather futile to try to study it when there are no sure means by which to replicate it.
Consider Twilight Sparkle. Used to experimenting and conducting research, such a notion would be second nature to her. As such, and taking into account her extraordinary abilities and her years of experience, it is a perfectly reasonable and expected reaction for her to automatically derive the logical, statistical conclusion when presented with a given set of results.
Consider Princess Celestia. Not the real one, but the one existing inside Twilight Sparkle's mind. She is Twilight's inspiration. She is the one Twilight looks up to. She is, while not flawless, certainly above the average pony. She has, after all, ruled Equestria for hundreds of years. Given the country's prosperity, it is undeniable that she must be a great ruler. Furthermore, she has been Twilight's personal teacher. Everything Twilight achieved, she achieved thanks to her studies under Celestia, and thanks to her guide. And when considering Twilight's rather remarkable results, it is only natural to conclude that Celestia must be a great teacher.
Consider thermal shock. Not the pony, we will get to him in a later chapter, but the phenomenon. It is what happens when an object at a given temperature is exposed to an environment with a drastically different one, without time to slowly adjust to the change. This causes different parts of the object to react differently depending on the exposure to the outside environment, either expanding or contracting, which may ultimately result in the object itself breaking.
Consider an idea, a concept, a series of categorised opinions and convictions related to a single topic or subject. Consider that idea as the object, and the world of facts as the environment. If, when confronted with the truth, one finds it opposite to the preconceived notion possessed on the matter, something similar to thermal shock might occur. While not certain, a violent reaction is likely to result, whether it be denial of the truth or internal turmoil at the revelation. Simple assimilation is unlikely, and increasingly so the more deeply ingrained and central the concept was.
Consider Twilight Sparkle. She believes in the existence of something that is considerable as good. She believes truth to be a part of this. She believes the right choice is to believe what evidence leads to believe, rather than what we would wish to be the reality of the situation.
Still, some things are truly, deeply rooted in an individual's mind, and it takes time, self-reflection, and often some sort of physical demonstration to finally convince them of the facts' validity.
And I have to be thankful for that, because otherwise I would never have gotten out of that box.