Last altered 1/9/14
John Barwise and John Etchemendy,  Language, Proof and Logic
For the Tarski's World part of LP&L, a standard interpretation is used of various sized polyhedra on a chessboard. Here is a link to their screenshot of it Tarski's World.
Here we are just trying a few samples to see if the software is running correctly.
[In the widget below:- Click once to select, click again to un-select. Select one item to extend the Tree, select two to close a branch. Select one or two for extending by Analytic Consequence (depending what inference you are trying for). Select two for extending with identity.]
1. ∃x(Cube(x)∧∀y(Cube(y) → y=x)) ∴ ∃x∀y(Cube(y) ↔ y=x) (p.377)
2. SameRow(a,a), a=b, b=c ∴ SameRow(a,c)