Not because they are the source of truth, on the contrary, they are usually downright misleading. But it is useful to understand what it is people want you to believe, and why.

You also have to keep in mind that neither propaganda or advertising are necessarily deliberate lies. Sometimes the source actually believes what they are saying, and are doing their best (or so they sincerely believe) to inform you so you will interpret the facts as they do. At other times, they may be deliberately and maliciously biased (usually for the most noble of reasons), and the reporting, either carefully selected, emphasized or arranged to get across a certain POV. The individual factoids may be absolutely verifiable truth; in fact, the good propagandist or marketer (the two terms are equivalent, so I will no longer use both) may be counting on you to check his facts.

The point is that what we call truth is always a matter of interpretation. Sure, you can say precisely that a plane crashed and there were X casualties. But that isn't what we really want to know, is it? We need to understand if the plane was mechanically defective, or the crew unprepared or incompetent, or if the government safety regulations were adequate, or if terrorists brought it down. In some cases, we can point to a direct cause, like weather, but real accidents usually result from a combination of circumstances; not all planes crash because of bad weather, and not all bad weather results in crashes. Perhaps the pilot was overworked and fatigued, or the runway lights were not properly functioning. Sometimes the truth is in between, or a combiantion of factors. In fact, that's the way it usually is.

Another factor you have to be careful of is the tendency of the human mind to seek a simple and comprehensive answer to a question. There may be none, or we may be asking the wrong question, or our ideological biases have us hyper-sensitive to treachery and foul play; when sometimes, shit just happens.

Study history, particularly, study historians' interpretations of history. You can tell precisely when a battle or earthquake occurs, but do we know why it happened, or what its ultimate result was? Historians are constantly coming up with the "real" reason the Civil War was fought. The people who fought it know why, the winners and losers know why, each generation of historians has a theory, and journalists and commentators from other countries and eras have their opinions. And very often all these takes on it are different, sometimes substantially.

This is particularly obvious (but not restricted to) in military history. Did the General execute a brilliant pincer movement? Or did he foolishly divide his forces? Was he wise to seize the initiative and go on the offensive, or was it better to let the enemy commit himself irrevocably to a strategy and then respond to it appropriately? Is the careful, methodical tactician going to be the victor, or the brilliant and unorthodox strategist? Did the Commander disengage and withdraw just in time, or did he fail to press on when victory was just within his grasp? Clearly, it doesn't depend on what the general does, it only depends on whether it works or not, and we won't know that until after the smoke clears. But by then, the knowledge is too late to be useful; after all, in the next war, circumstances will not be the same.

We often confuse the truth and our perception of it, and fact for interpretation. Does this mean we should wring our hands and do nothing? Of course not. We need to act, but we must also realize sometimes it pays to delay, and sometimes it pays to avoid the decision altogether, and we never know for sure which. Luck plays a great, but not necessarily decisive, role in everything we do. Sometimes we just have to rely on judgement and intuition, experience and training. But there are no guarantees, either..

But you know disaster is near the day you convince yourself you have it all figured out, that you understand exactly what is going on, and that the other guy is wrong because...well, he's just wrong, because you have it all figured out and understand what is going on.... 8)