I'm trying to make a Tarski World for this structure:
$$\forall x (Triangle(x) \iff \exists y (Square(y) \land AboveOf(x,y)))$$
I think that it means the following:
- Element is a triangle if and only if there is a square below it. So every triangle must have squares below it.
- There is a square that is below some element if and only if that element is a triangle. So no square should be below any elements that are not triangles.
However, the answer has a picture that has one square above the other. Why is that?