English: Visual proof of Balinski's theorem: if fewer than d vertices (yellow) are removed from the graph of a d-dimensional polytope, then it is possible to find a nontrivial function whose zero set (the blue plane) includes another vertex (green). Then the simplex method can be used to find paths from the selected vertex to the two extreme points of the linear function, and from every other vertex to at least one extreme point, connecting all of the remaining vertices. Therefore, one must remove at least d vertices in order to disconnect the remaining graph.