Smack me. I suppose it's all in interperetation..... I still feel that since it doesn't behave like the others, it shouldn't be classified with the others, but so what. As the game evolves, I will be able to make more accurate destinctions.
Really it comes down to this: the only real difference we know of between life/death magic and the other four elements is that there are no life/death shards. So if you don't consider life/death magic to be a magic element, then you believe that to be an element there must be a corresponding shard type. That's just silly to me... The earth, air, water and fire elements all have different sources - they just all happen to be bound up in shards. If the ancient powers that were decided to bind the different magical elements into separate vessels (one might have been in a crystal, maybe one in a table, they could have bound one in a race of people, etc). Those four elements happened to be bound into crystals, while life and death magic are not.
And ultimately what really matters from a gameplay perspective is the function. From everything we know, life/death will function exactly like the other elements regarding spells and the like. Seriously, anyone who complains that life/death don't count as magical elements or schools because they don't come from shards is being a nit-picking baby whingeing for the sake of it. The notion that some people might say "you don't get life/death magic from a shard, it's not an element!" even though everything else about it functions exactly like the rest of the elements just makes me mad. Especially if those same people would all of a sudden breathe easily and say "phew, now Elemental is five elements just like good 'ol MoM" if Stardock decided to include life/death shards.
If you go around saying that thematically there are four elements and one other 'school' of magic, fine - I couldn't care less. But if anyone actually tried to accuse Stardock of false advertising by claiming there to be five magical elements in their game because one of them isn't based around shards - ugh.