6 In August 1934, addressing Ourselves to a delegation of the International Federation of the Motion Picture Press, We pointed out the very great importance which the motion picture has acquired in our days and its vast influence alike in the promotion of good and in the insinuation of evil, and We called to mind that it is necessary to apply to the cinema the supreme rule which must direct and regulate the great gift of art in order that it may not find itself in continual conflict with Christian morality or even with simple human morality based upon the natural law. The essential purpose of art, its raison d'être, is to assist in the perfection of the moral personality, which is man, and for this reason it must itself be moral. And We concluded amidst the manifest approval of that elect body - the memory is still dear to Us - by recommending to them the necessity of making the motion picture "moral, an influence for good morals, an educator".
Source: Vigilanti Cura (Vatican.va)