MR. MOORE'S "Principia Ethica" affords repeated illustration of the qualities which have distinguished his earlier and more fugitive contributions to philosophy; it is eminently ingenious and acute, and no less eminently irritating and, as it must appear to readers not convinced of- the truth of its author's peculiar tenets, wrong-headed. To some extent, no doubt, irritation is bound to be caused by any book which has at once the courage to assail...