There are two quite different kinds of influence to which the formation of an ethical doctrine may be due. In the first place, there are the moral sentiments and opinions of the community and of the moralist himself; and, in the second place, there are the scientific and philosophical doctrines accepted by the writer or inspiring what is loosely called the spirit of the time. In most ethical movements the two kinds of influence will be found co-operating, though the latter is almost entirely absent in some cases. The incoherence of popular opinions about morality is a potent stimulus to reflexion, and may of itself give rise to systematic ethical enquiry. This is more particularly the case when a change of social conditions, or contact with alien modes of life, force into light the inadequacy of the conventional morality. In such a case the new ethical reflexion may have a disintegrating effect upon the traditional code, and give to the movement the character and importance of a revolution. The reflective activity of the Sophists in ancient Greece--a movement of the deepest ethical significance--was in the main of this nature. It consisted in a radical sifting and criticism of current moral standards, and was due almost entirely to the first class of influences, being affected only in the slightest degree by scientific or philosophical ideas. Influences of the same kind combine with science and philosophy in moulding the ethical thought of the present day. Contemporary ethical speculation is by no means exclusively due to the thinkers who attempt to arrive at a consistent interpretation of the nature of reality; and it has features which constantly remind us how closely moral reflexion is connected with the order and changes of social conditions. Every age is no doubt apt to exaggerate its own claims to mark an epoch. But, after a century of achievements in applied science, there seems little risk of error in asserting that the world is now becoming conscious as it never was before of the vast power given by material resources when under the control of a cool intelligence. And in the competition of nations it is not surprising that there should be an imperious demand for the most alert and well-trained minds to utilise these resources in war and in industry. It is not surprising; nor would it be a fit subject for regret, did not the concentration of the outlook upon material success tend to the neglect of 'things which are more excellent.' Writing many years ago J.S. Mill remarked that "hitherto it is questionable if all the mechanical inventions yet made have lightened the day's toil of any human being." [1] [Footnote 1: Political Economy, Book iv. chap. vi. § 2.]