four preceding means, qualities which raised their authority very
high, so much so that those who succeeded them were willing rather
to acquiesce in their opinions, than to seek better for themselves.
The chief question among their disciples, however, was as to whether
we ought to doubt of all things or hold some as certain,--a dispute
which led them on both sides into extravagant errors; for a part of
those who were for doubt, extended it even to the actions of life,
to the neglect of the most ordinary rules required for its conduct;
those, on the other hand, who maintained the doctrine of certainty,
supposing that it must depend upon the senses, trusted entirely to
them. To such an extent was this carried by Epicurus, that it is
said he ventured to affirm, contrary to all the reasonings of the
astronomers, that the sun is no larger than it appears.

It is a fault we may remark in most disputes, that, as truth is the
mean between the two opinions that are upheld, each disputant
departs from it in proportion to the degree in which he possesses
the spirit of contradiction. But the error of those who leant too
much to the side of doubt, was not followed for any length of time,
and that of the opposite party has been to some extent corrected by
the doctrine that the senses are deceitful in many instances.
Nevertheless, I do not know that this error was wholly removed by
showing that certitude is not in the senses, but in the
understanding alone when it has clear perceptions; and that while we
only possess the knowledge which is acquired in the first four
grades of wisdom, we ought not to doubt of the things that appear to
be true in what regards the conduct of life, nor esteem them as so
certain that we cannot change our opinions regarding them, even
though constrained by the evidence of reason.