When I was in primary school, one of my school teachers (Mr Hanley) took it upon himself to encourage our intellectual curiosity. This was done through teaching us about classical greek geometry, telling us fables and stories with a moral lesson, promoting mathematics and science and teaching us about other cultures.
In hindsight, one of the traits that he tried to instill in us was skepticism - and I guess this trait found its home in me, and has inspired me ever since. He once told us a story of a king who asked his courtiers to answer a question: Why, when a fish dies, does it weigh less than when it was alive? The story goes that, no matter what reasons people came up with, none of the answers were accepted by the king.
Eventually one scientist decided to empirically test the idea, and weigh a fish when alive and when dead. His answer to the king was that his assertion was incorrect, and that a fish doesn't weigh less when it dies. This was the answer that the king was looking for.
My presumption is that this parable is related to the fact that while a live fish has neutral buoyancy, dead fish will often float on the surface of the water. Many fish use a swim bladder filled with gas to maintain neutral buoyancy, and when the fish dies that balance is no longer maintained. Often that will result in an excess of gas, and a fish fill float to the surface. Of course, being a light gas, which has presumably come about from biological processes within the fish, the weight of the fish doesn't change - it's just the density that changes. The same mass of fish takes up more space as more of its solid is converted to gas (through baterial breakdown, etc).
The obvious lesson of this story is that we should question things, and not take what we are told for granted. As a skeptic, I now know that this fallacy is a form of Begging the Question - that the question contains an invalid assumption, and simply asserts that the assumption is true. We must be free to question these assertions, and must be wary about what we accept as fact.
A more subtle lesson is that we should be more ready to question things when they don't make sense. In this case, the idea that a fish would weigh less when it's dead, despite the fact that it's made of the same material, seems to be nonsensical. On a practical level, we can't go about questioning everything in our daily lives - but the flip side of this is that we need to be careful not to trust too much. Questioning things that don't make sense is okay.
There's another lesson to be learned here as well - about authority, and the questioning of that authority. Often people in positions of authority aren't questioned enough, and power allows people to make claims that go unchecked - either because of an assumption that the person in power is correct (after all, how did the person get to where they are if not for them having an ability to be right about things), or a fear of the repercussions when the authority figure is questioned.