In the bathroom, I talked with my son about the congruency of triangles. He's only six years old and, of course, was not seemed to fully understand the most important part of Mathematics. That is, Math is all about explaining something as objective as possible. Some says that you'll never understand any part of Math until you can explain that, but if you ask me, it's the explanation itself that Mathematics is. I wish I had realised that at least twenty years ago...