passes
away. This original, naive and very nearly correct philosophy of the
world is that of the old Greek philosophers and was first put in a
very clear form by Heraclitus. Everything is and yet is not, since
everything is in a state of flux, is comprehended as undergoing
constant modification, as eternally existing and disappearing. But
this philosophy, correct as it is as regards phenomena in general,
viewed as a picture, is insufficient to explain the individual
phenomena of which the picture of the universe is composed, and as
long as we cannot do that we are not clear about the general picture.
In order to study these individual phenomena we are obliged to take
them out of their natural or social connection, and examine each of
them by itself according to its own form and its particular origin and
development. This is the task of natural science and historical
investigation, branches of discovery to which the Greeks of classical
times assigned a subordinate place for very good reasons, since they,
first of all, had to collect the material. The beginning of an exact
observation of nature was made first by the Greeks of the Alexandrine
period, and was later developed further by the Arabs in the Middle
Ages. True natural science hence dates from the second half of the
fifteenth century, and from then on has advanced at a constantly
growing rate. The dissection of nature into its separate parts, the
separation of different natural events and natural conditions into
certain classes, the examination of the interiors of organic bodies
with respect to their manifold anatomical forms, furnished the
fundamental reasons for the progress in a knowledge of nature which
the last four hundred years have brought in their train. But it has
caused us occasionally to drop into the habit of regarding natural
phenomena and events as entities, apart from the great universal
interrelations, and therefore not as moving but quiescent, not as
changeable in their essence but fixed and constant, not in their life
but in their death. And hence, just as happened with Bacon and Locke,
this point of view has been carried over from science into philosophy,
and has constituted the specially narrow view of the last century, the
metaphysical mode of thought.

For the metaphysician, things and their pictures in the minds,
concepts, are separate entities, one following the other without any
regard to each other, stable, rigid, eternally fixed objects