I only just realized the point behind the Liskov Substitution Principle - a rather interesting point, from a software design perspective. I once thought that the material we were covering in the OO design unit was quite superflous, and in my arrogance thought that most relevant topics must surely be intuitive and not worth the lengthy tomes that lie shelved in the library. I see now just how wrong I was. I can't say that I will enjoy the rigmarole of design, but I think I have gained a little more respect for it as a formalized process (obviously I don't think there's anything wrong with design itself; I just had qualms with UML diagrams, and questioned their purpose). What gets me down is the fact that we were spared the interesting examples that are abound on the net, and instead were treated with a dry, theoretical statement that did not make any conceputal sense. The lecturer said words to the effect of "Now we get to the interesting stuff" when he introduced it, but his treatment led me to believe it was very ordinary, and somewhat obvious. It's strange, because the lecturer definitely knows what he's talking about, yet his teaching is somewhat lacking.