I've just hit a new stupidest online debate I've ever been trapped in. We had started off in the context of things you could add to coffee to change its taste, preferably for the better. My position: it's fair to consider sugar as a kind of spice. My opponent's position: a spice is, according to the Oxford English Dictionary, ``an aromatic or pungent vegetable substance used to flavour food'' and therefore sugar, ``a sweet crystalline substance obtained especially from sugar cane and sugar beet'' is the opposite of a spice.
I admit I tend to view definitions outside mathematics as open sets, and you wouldn't have to work hard to get me generous enough to let you bring in salt under the general category of spices. But I still don't get what part of the definition of ``spice'' given there isn't satisfied by ``sugar''. I grant that it's often used as a more fundamental baking ingredient than other spices are, but that doesn't seem like enough to dismiss it, particularly considering sugar is often used decoratively or to add a bit more taste to an already finished product (like adding a sprinkling of sugar onto a doughnut). Since we were in agreement about the important properties that make something a spice, and that make sugar, this makes the range of conclusions drawn all the more fascinating and yet, fundamentally, sad.
As I don't want another round of the fight, I should admit I don't think I have a very strong case -- the fact that ``sugar and spice'' is a common phrase indicates they're usually thought of as somewhat distinct -- and it's not one I would try standing up to a hostile customs officer with. But I would say sugar's in the same family of ingredients as cinnamon, pepper, and capsicum. Up against the contention ``you don't keep sugar in your spice rack, do you?'' I think my stance that sugar meets the important properties of a spice stands pretty well. I don't even have a spice rack, although answering that honestly makes it sound like I'm the one being difficult.
Trivia: The Dutch East India Company's original (1602) commission gave it a total monopoly on the Dutch spice trade for 21 years. Source: Nathaniel's Nutmeg, Giles Milton.
Currently Reading: The Adventures of Tom Sawyer, Mark Twain.