 Indeed, one can recognize the explanatory power of a theory without taking it to be true. Van Fraassen points out that theories can explain well even if they are false. Newton’s theory of gravitation explains the motion of the planets and the tides, “Huygens’s theory explained the diffraction of light, Rutherford’s theory of the atom explained the scattering of alpha particles, Bohr’s theory explained the hydrogen spectrum, Lorentz’s theory explained clock retardation.” But none of these theories is now thought to be true.