Judgments Of Probability

If I asked what you would expect to happen of you noticed dark storm clouds outside, how would you answer?  You would likely respond by stating that it will probably rain, of course.  But on what basis do you expect such a thing to occur?  On the basis of past experiences which have accumulated to the point where you anticipate rain each time you see dark storm clouds.  After a certain number of times where you saw dark clouds followed by rain, you began to judge it highly probable that rain would descend every time such clouds appeared.

Probability and probability alone is the basis for our
claims and expectations about future events.  In some
cases, such as when one is rolling dice, one can know
exactly what probabilities exist given set conditions,
but many probability judgments are far from absolutely
certain.

People can only make estimates of probability about the future based upon past precedents (except in some cases like the dice example above).  In other words, they can only predict certain events like someone falling to the ground after he or she jumps if they have experienced similar outcomes in the past.  After seeing the same result many times--that someone who jumps falls back to the ground every time he or she jumps--people conclude that every time someone jumps that person will inevitably fall back down.  These observations allow scientists to make informed predictions about the outcomes of experiments because data from past events appear to generally, or universally in some cases, point towards  repeatable results.  Indeed, the entire scientific method depends on this system and the continual observation that the same outcomes happen under certain conditions.  Apart from this, any illumination of the world from science would shatter.  But our inescapable reliability on probability when forecasting the future also means that, hypothetically speaking, we might awake one day to find that the sun has not risen, or that our close friends never loved us to begin with, or that pushing the brake pedals of our cars speeds up our vehicles instead of slowing them down.  Since we can only have informed probability about a great many things, we have no way to verify that expected outcomes necessarily must happen given a set of conditions or experiences.

So, how does probability affect our epistemology?  Quite a bit, actually.  Start listing out beliefs and statements to yourself and if you assess them you will quickly find that the closest we can come to verifying or falsifying many of them is to make a case for or against them which hinges on probability estimates.  A developed philosophy called probabilism holds that we should settle for the most probable of two or more options in cases where absolute certainty is unattainable, encouraging this type of thinking.  Of course, since we do not and cannot have absolute certainty about a great number of things (whether or not the sun will rise tomorrow, if a significant other loves us, etc), the only avenue open to us is estimating the probability of a given premise or claim based upon our awareness of other facts.  We cannot know if things in this category are true or false, but we can know that they seem more probable considering our other knowledge.

Now, probability estimates are often extremely subjective--again, this is untrue in certain conditions, like in the dice example; one can know that if there are six sides to a die, if the die is not weighted on one side, if the sides do not change, and if one of them must be showing at the top, then there is an exactly 1/6 chance that any of the sides will end up on top.  Because judging probability often relies on recollection of our experiences and perceptions and because our experiences and perceptions are often subjective and different, it is no surprise to me that many people find different possible truths more probable than others do.  Someone who has studied history extensively will view as historically probable things entirely different than what a historically uneducated person might think probable, and vice versa.  If a person has found that every foreigner he or she has met acted rudely, that person may judge it probable that most or all foreigners will act in a rude manner (though this commits the fallacy of composition), while someone with pleasant experiences with foreigners will not share this expectation (though rudeness has to do only with individual personality or cultural conditioning and not being a foreigner).  Both of these examples demonstrate that since judgments of probability are based on experience and experience varies from individual to individual, probability estimates themselves are often varied due to the subjectivity of the experiences people derive them from.  Also, assigning a mathematical percentage to a probability claim, such as "I have 76% certainty that this outcome will result", only further highlights the utter subjectivity of many of these claims.  What I call 97% probability or certainty might be perceived as 88% probability to someone else, and 73% to someone else, 56% to someone else, and so on.

The subjectivity of probability serves as a powerful reason why, when the circumstances allow for it, seekers of truth should try to avoid making either elaborate or intuited probability judgments--because even the measure of certainty that probability offers us often remains uncertain.  Yet many existing human beliefs rest entirely on perceived probability, not logical certainty.  Entire disciplines like history, science, criminal investigation and even most of our expectations for our everyday lives hinge on probability to a large degree.  Clearly, some things seem more probable to us than others, but we need to exercise care when making claims about future events, for we do not always have as much to ground our predictions with as we may believe.  We will find judgments of probability necessary in many arenas, so we need to cautiously assess our experiences to ensure that we do not misunderstand them and thus infer improbable or fallacious expectations.


Summary of observations:
1. Predictions of the future hinge on judgments of probability derived from past precedents unless specific conditions are known.
2. Anything believed in the absence of absolute certainty is believed because it is judged more probable than its negation or possible alternatives.
3. Probability estimates are often subjective because the experiences we base them on are subjective and varying.