Actually I was judging based on body structure and the surrounding objects. I think I can guesstimate how tall a chair is. Sometime's stuff that seems so obvious and simple to me baffles the less fortunate I guess, you guys even think it's magic and random guessing it's kinda cute.
You do realize that chairs have different backing heights, right? The bar stools by the island in my kitchen have a backing that is roughly 8" tall, while the chairs in my dining room are about 1.5' tall. And then the folding chairs by my poker table are about 12" tall.
Your argument is completely invalid. Unless you're an expert on chairs, in which case I'm sorry to question your flawless intelligence!