What Makes A Sandwich A Sandwich?

Well, if you believe the myth it’s a piece of bread or two (there is considerable debate on this point) with a stuffing that you can eat without utensils while playing cards and not getting them greasy.

On a deeper level, what is anything?

Plato posited “Absolutes” which carried within them the definition of the essential elements that made some thing, say a Chair, a Chair regardless of superficial variation.

My question is- “Can you sit on it?”