igated
by the Comparative Method. Again, the recorded history of a nation, and
of all its institutions, followed backwards, comes at last to an end:
then the antecedent history must also be supplied by the Comparative
Method; whose special use is to indicate the existence of facts for
which there is no direct evidence.

This method rests upon the principle that where the causes are alike the
effects will be alike, and that similar effects are traceable to similar
causes. Every department of study--Astronomy, Chemistry, Zoology,
Sociology--is determined by the fact that the phenomena it investigates
have certain common characteristics; and we are apt to infer that any
process observed in some of these phenomena, if depending on those
common characteristics, will be found in others. For example, the
decomposition, or radio-activity, of certain elements prepares one to
believe that all elements may exhibit it. Where the properties of an
object are known to be closely interdependent, as in the organisation of
plants, animals and societies, we are especially justified in inferring
from one case to another. The whole animal Kingdom has certain common
characters--the metabolic process, dependence upon oxygen, upon
vegetable food (ultimately), heredity, etc., and, upon this ground, any
process (say, the differentiation of species by Natural Selection) that
has been established for some kinds of animal is readily extended to
others. If instead of the whole animal Kingdom we take some district of
it--Class, Order, Family--our confidence in such inferences increases;
because the common characters are more numerous and the conditions of
life are more alike; or, in other words, the common causes are more
numerous that initiate and control the development of nearly allied
animals. For such reasons a few fragmentary remains of an extinct animal
enable the palaeontologist to reconstruct with some probability an
outline of its appearance, organisation, food, habitat and habits.

Applied to History, the Comparative Method rests upon an assumption
(which the known facts of (say) 6,000 years amply justify) that human
nature, after attaining a recognisable type as _homo sapiens_, is
approximately uniform in all countries and in all ages, though more
especially where states of culture are similar. Men living in society
are actuated by similar motives and reasons in similar ways; they are
all dependent upon the supply of food and therefore o