THE STORY OF PHILOSOPHY2 The Lives and Opinions

i 28 THE STORY OF PHILOSOPHY
order of nature; the more it understands its forces or strength, the better it
will be able to direct itself and lay down the rules for itself; and the more it
understands the order of nature, the more easily it will be able to liberate
itself from useless things; this is the whole method.
Only knowledge, then, is power and freedom; and the only permanent
happiness is the pursuit of knowledge and the joy of understanding.
Meanwhile, however, the philosopher must remain a man and a citizen;
what shall be his mode of life during his pursuit of truth? Spinoza lays
his actual
down a simple rule of conduct to which, so far as we know,
behavior thoroughly conformed:
i. To speak in a manner comprehensible to the people, and to do for them
all things that do not prevent us from attaining our ends. . . . 2. To enjoy
only such pleasures as are necessary for the preservation of health. 3. Finally,
to seek only enough money ... as is necessary for the maintenance of our
life and health, and to comply with such customs as are not opposed to
what we seek. 31
But in setting out upon such a quest, the honest and clearheaded
philosopher comes at once upon the problem: How do I know that my
knowledge is knowledge, that my senses can be trusted in the material
which they bring to my reason, and that my
reason can be trusted with
the conclusions which it derives from the material of sensation? Should
we not examine the vehicle before abandoning ourselves to its directions?
Should we not do all that we can to perfect it? "Before all things/' says
Spinoza, Baconianly, "a means must be devised for improving and clarifying
the intellect." 32 We must distinguish carefully the various forms of
knowledge, and trust only the best.
First, then, there is hearsay knowledge, by which, for example, I know
the day of my birth. Second, vague experience, "empirical" knowledge in
the derogatory sense, as when a physician knows a cure not by any
scientific formulation of experimental tests, but by a "general impression 9 *
that it has "usually" worked. Third, immediate deduction^ or knowledge
reached by reasoning, as when I conclude to the immensity of the sun
from seeing that in the case of other objects distance decreases the apparent
size. This kind of knowledge is superior to the other two, but is yet
precariously subject to sudden refutation by direct experience; so science
for a hundred years reasoned its way to an "ether" which is now in high
disfavor with the physicist elite. Hence the highest kind of knowledge is
the fourth form, which comes by immediate deduction and direct per-
number in the
ception, as when we see at once that 6 is the missing
proportion, 2:4: :s:x; or as when we perceive that the whole is greater
than the part. Spinoza believes that men versed in mathematics know
most of Euclid in this intuitive way; but he admits ruefully that "the
**"De Emendatione, Everyman edition, p. 231.