[jmalicki]

Not at all. It's called learning computer science. Just like you can do calculus without simulation, you can understand the semantics of a computer program without running it. It might make it harder, but running it is only a didactic tool - as Knuth did, you should be able to prove it correct without ever running it.

[dnnddidiej]

Yes but not everyone learns like that. Some people need to feel something before learning the theory. It makes the theory easier to digest.