The ancient civilised peoples appear in history with a fully-developed system of time-reckoning--the Egyptians with the shifting year of 365 days, which comes as nearly as possible to the actual length of the year, counting only whole days and neglecting the additional fraction; the Babylonians and the Greeks with the lunisolar, varying between twelve and thirteen months and arranged by the Greeks from the earliest known period of history in the cycle of the _Oktaeteris_. It has always been clear that these systems of time-reckoning represent the final stage of a lengthy previous development, but as to the nature of this development the most daring hypotheses have been advanced. Thus, for example, eminent philologists and chronologists have believed the assertion of Censorinus, Ch. 18, and have supposed that the _Oktaeteris_ was preceded by a _Tetraeteris_, even by a _Dieteris_. It may indeed at once be asserted that such a hypothesis lacks intrinsic probability. To account for the early development hard facts are needed, and unfortunately these, especially in the case of the Greeks, are extremely few. Where they are required they must be sought elsewhere. Setting aside all ingenious but uncertain speculations, our only practicable way of proceeding is by means of a comparison with other peoples among whom methods of time-reckoning are still in the primitive stage. This is the ethnological method which is so well-known from the science of comparative religion, but the claims of which have been so vigorously contested upon grounds of no small plausibility. Fortunately this dispute need not be settled in order to prove the validity of the comparative method for an investigation into the origin and development of methods of reckoning time. The gist of the dispute may be expressed as follows:--The ethnological school of students of comparative religion assumes that the intellect of the natural man can only master a certain quite limited number of universal conceptions; from these spring more and more abundantly differentiated and complicated ideas, but the foundation is everywhere the same. Hence our authority for comparing the conceptions of the various peoples of the globe with one another in order to lay bare this foundation. The opponents of the school deny the existence of these fundamental conceptions, and maintain that the points of departure, the primitive ideas of the various peoples, may be as different as the peoples themselves, and that therefore we are not authorised in drawing general conclusions from the comparison or from the fundamental conceptions themselves.