On page 13-3 of his Lectures on Physics, Feynman says: "We have seen that there is a force on a wire in the presence of a magnetic field, produced, say, by a magnet. From the principle the action equals reaction we might expect that there should be a force on the source of the magnetic field, i.e., on the magnet, when there is a current through a wire.*" In the footnote, it says:"We will say later, however, that such assumptions are not generally correct for electromagnetic force." Does that mean that for electromagnetic forces, the law of action and reaction does not hold? If so, where does Feynman discuss this "later"? Also, is there a simple example where the law of action and reaction does not hold? Any help would be greatly appreciated. Thank You in Advance.