"How can you arbitrate what is a pie and what is a tart?"
"The concepts are only valid to us based on their nomative labels and words are not objective in any sense. If another culture inverts the words that does not make them wrong, nor would it if one man were to invert the words. The very concepts themselves are only subjective networks in which people can share the same ideas and concepts."
(JeruWar and Piss,
Thu 28 Feb 2008, 21:55,
archived)
Obviously we weren't hoping to place any kind of objective value on the labels 'pie' and 'tart'.
We were more interested in the every day usage. I believe our conclusion was that if it is fully pastry topped it is a pie, otherwise, it is a tart. In the special case of lattice tops, if the lattice covers more than, say, 50% of the area of the surface, it's a pie.