sychical development begins with the homogeneity of all the
individual members of a society and, through heightened psychical activity,
advances in the form of a continually increasing differentiation of the
individuals (this is akin to the Spencerian formula). This process,
evolving psychical freedom from psychical constraint, exhibits a series of
psychical phenomena which define successive periods of civilisation. The
process depends on two simple principles, that no idea can disappear
without leaving behind it an effect or influence, and that all psychical
life, whether in a person or a society, means change, the acquisition of
new mental contents. It follows that the new have to come to terms with the
old, and this leads to a synthesis which determines the character of a new
age. Hence the ages of civilisation are defined as the "highest concepts
for subsuming without exception all psychical phenomena of the development
of human societies, that is, of all historical events."[245] Lamprecht
deduces the idea of a special historical science, which might be called
"historical ethnology," dealing with the ages of civilisation, and bearing
the same relation to (descriptive or narrative) history as ethnology to
ethnography. Such a science obviously corresponds to Comte's social
dynamics, and the comparative method, on which Comte laid so much emphasis,
is the principal instrument of Lamprecht.

19. I have dwelt on the fundamental ideas of Lamprecht, because they
are not yet widely known in England, and because his system is the
ablest product of the sociological school of historians. It carries
the more weight as its author himself is a historical specialist, and
his historical syntheses deserve the most careful consideration. But
there is much in the process of development which on such assumptions
is not explained, especially the initiative of individuals. Historical
development does not proceed in a right line, without the choice of
diverging. Again and again, several roads are open to it, of which it
chooses one--why? On Lamprecht's method, we may be able to assign the
conditions which limit the psychical activity of men at a particular
stage of evolution, but within those limits the individual has so many
options, such a wide room for moving, that the definition of those
conditions, the "psychical diapasons," is only part of the explanation
of the particular development. The heel of Achilles in all historical
speculati