I was working on a problem out of Griffiths, and have become a bit confused. The problem is regarding to Earnshaw's theorem, which states that a particle cannot be held in stable equilibrium by electrostatic forces. (3.2 for anyone with the text). He suggests a cube with a positive charge on each of the eight corners, and asks what would happen to a positive charge placed in the center. It seems to me that the charge could stay at rest if it were somehow perfectly placed between all the corners, but that's not really possible so it is not worth considering. Earnshaw's theorem state that it could not be contained and will be removed. However, what if the corners became really close, or there were more positive charges... Wouldn't it simply be contained due to repulsion from the sides? That may just be the answer, but I think I've become a little bit confused. There's also the matter of the electric potential. The middle would be the point of highest electric potential. He warns against thinking of electric potential as being 'potential energy' but is it correct to assume the particle would move to a point of lower electric potential? Thanks for your time, and sorry if this is a bit scatter-brained. I found I was unclear about several things when writing this.