Every decision is taken in the context of countless conditions. The number of possible reverberations that might result from any significant life decision is infinite, and the possibilities usually range from total success to utter failure. When you also count in the potential effects on others, and their probable reactions, trying to figure it all out logically is an impossibility and often leads to complete inability to make any decision at all. There are two possible kinds of response to this situation. Some declare that you just can never think it through and must rely on some kind of intuition or “direct knowing” or some such. This is just giving up, and the likelihood of making anything close to the optimal decision is no greater than plain chance. This is not much of a problem in the personal sphere where your actions will affect only a limited number of people, but in the public sphere it just is not good enough. If we are to make laws that everyone must obey and decisions that will affect everyone (and to live in a society we must do that) we owe it to them to base those laws and decisions on the most reliable basis possible.
This raises one of the most fundamental philosophical questions: “How do we know what we know?” The reason this question is so important is because the only way we can justify society’s abridgment of citizens’ freedom is if we can be morally certain that there is a strong and valid reason for it. There is no such thing as absolute certainty about anything, but in order to balance a societal need against the citizen’s freedom of action we need to know at the very least four things: what is the degree of harm being avoided; what is the severity of the restriction on freedom; what is the likelihood of the harm occurring; and how certain are we that the danger is real?
There are countless examples in history of measures being taken to counter a perceived danger that turned out in the end never to have been a danger at all. The Cold War was largely based on a gross overestimation of the capabilities and hostile intent of the USSR. 9/11 precipitated a series of government actions the echoes and aftershocks of which are still roiling the world (and inconveniencing the traveler) in 2017, which have cost us untold lives and treasure, and virtually none of them, I would be willing to bet, had any effect whatever upon the likelihood of another such event. So clearly it is vitally important to know what degree of credibility to give to any given piece of information.
We must recognize just how difficult it is to be certain of something. Things which seem self-evidently true turn out to be completely false. Things that seem quite obviously to be caused by a particular circumstance turn out to be caused by something quite different. We give great weight to our own personal experience, and the experiences of our friends and acquaintances, forgetting that we and they may very well not be typical of the world at large.
Fortunately this problem is not new. People have been thinking about it for centuries, and have come up with various solutions. Religion, in all of its varieties, is one solution. God will tell us what is right and what is wrong, and it is not up to us mere mortals to inquire into such matters. The difficulty with this solution is that there is by definition no way to verify the truth of what God says. You just have to have faith that it is true. Unfortunately we cannot even verify convincingly that such a concept as God even exists, and still less can we be certain that any alleged communication fro that source is even genuine, to say nothing of the impossibility of verifying its correct meaning. If your personal experience runs counter to what God says in any aspect at all, the whole edifice is then suspect, and you are left with no certainty.
Then there is folk knowledge, also known as old wives tales. Here we are on much more solid ground, as these remedies do represent accumulated experience and often study. The difficulty here is again the issue of verification. Too often old ideas persist long past the time when the original impulse for them is forgotten.
We might have direct personal experience of the matter, or perhaps have access to the combined experiences of others. Unfortunately this may be a poor basis upon which to draw a reliable conclusion. There may be something untypical about you and your acquaintances that make your experience quite different from that of others.
We may have a very strong intuitive flash that something is true. It just seems so right, answers so many questions, it just has to be true, right? Well, maybe. Certainly it could be true; many famous scientific discoveries came about through just such flashes of inspiration. But we do not hear the countless stories of the flashes of inspiration that turned out to be just plain wrong. The intuitive inspiration is just the start of the process. The real work is in testing the hypothesis to verify that it is in fact correct. Or more accurately to assess its degree of certitude.
Fortunately we have at our disposal the best tool ever invented by the mind of man for this purpose, and that tool is Science.