philosophy, and secondly, in relation to modern speculations.

(a) In the age of Socrates the mind was passing from the object to the
subject. The same impulse which a century before had led men to form
conceptions of the world, now led them to frame general notions of the
human faculties and feelings, such as memory, opinion, and the like. The
simplest of these is sensation, or sensible perception, by which Plato
seems to mean the generalized notion of feelings and impressions of sense,
without determining whether they are conscious or not.

The theory that 'Knowledge is sensible perception' is the antithesis of
that which derives knowledge from the mind (Theaet.), or which assumes the
existence of ideas independent of the mind (Parm.). Yet from their extreme
abstraction these theories do not represent the opposite poles of thought
in the same way that the corresponding differences would in modern
philosophy. The most ideal and the most sensational have a tendency to
pass into one another; Heracleitus, like his great successor Hegel, has
both aspects. The Eleatic isolation of Being and the Megarian or Cynic
isolation of individuals are placed in the same class by Plato (Soph.); and
the same principle which is the symbol of motion to one mind is the symbol
of rest to another. The Atomists, who are sometimes regarded as the
Materialists of Plato, denied the reality of sensation. And in the ancient
as well as the modern world there were reactions from theory to experience,
from ideas to sense. This is a point of view from which the philosophy of
sensation presented great attraction to the ancient thinker. Amid the
conflict of ideas and the variety of opinions, the impression of sense
remained certain and uniform. Hardness, softness, cold, heat, etc. are not
absolutely the same to different persons, but the art of measuring could at
any rate reduce them all to definite natures (Republic). Thus the doctrine
that knowledge is perception supplies or seems to supply a firm standing