posed the following question recently:

Is magic the defining element of fantasy? Discuss.

And in reply to this defined it thus:

Impossibility-within-currently-known-laws-of-nature is the defining element of fantasy, and magic is the most prominent (but not the only) presentation of that.

I think this might be quite a good definition of fantasy, but I’d like to open it out here for further debate, suggestions as to how it can be improved.