true idea.  (2) We must take care, as has been said, to separate such
perceptions from all those which arise from hearsay or unclassified
experience.  (3) Moreover, such mistakes arise from things being
conceived too much in the abstract; for it is sufficiently self-evident
that what I conceive as in its true object I cannot apply to anything
else.  (75:4) Lastly, they arise from a want of understanding of the
primary elements of nature as a whole; whence we proceed without due
order, and confound nature with abstract rules, which, although they
be true enough in their sphere, yet, when misapplied, confound
themselves, and pervert the order of nature.  (5) However, if we
proceed with as little abstraction as possible, and begin from primary
elements - that is, from the source and origin of nature, as far back
as we can reach, - we need not fear any deceptions of this kind.

[76] (1) As far as the knowledge of the origin of nature is concerned,
there is no danger of our confounding it with abstractions.  (2) For
when a thing is conceived in the abstract, as are all universal
notions, the said universal notions are always more extensive in the
mind than the number of individuals forming their contents really
existing in nature.  (3) Again, there are many things in nature, the
difference between which is so slight as to be hardly perceptible to
the understanding; so that it may readily happen that such things are
confounded together, if they be conceived abstractedly.  (4) But since
the first principle of nature cannot (as we shall see hereafter) be
conceived abstractedly or universally, and cannot extend further in
the understanding than it does in reality, and has no likeness to
mutable things, no confusion need be feared in respect to the idea of
it, provided (as before shown) that we possess a standard of truth.
(5) This is, in fact, a being single and infinite [76z] ; in other
words, it is the sum total of being, beyond which there is no being
found. [76a]

[77]  (1) Thus far we have treated of the false idea. We have now
to investigate the doubtful idea - that is, to inquire what can
cause us to doubt, and how doubt may be removed.  (2) I speak of
real doubt existing in the mind, not of such doubt as we see
exemplified when a man says that he doubts, though his mind does
not really hesitate.  (77:3) The cure of the latter does not fall
within the province of method, it belongs rather to inquiries
concerning obstinacy and its cure.

[78]  (1) Real doubt is never produced in the mind by the thing
doubted of.  (2) In other words, if there were only one idea in
the mind, whether that idea were true or false, there would be no
doubt or certainty present, only a certain sensation.  (3) For an
idea is in itself nothing else than a certain sensation. (4) But
doubt will arise through another idea, not clear and distinct
enough for us to be able to draw any certain conclusions with
regard to the matter under consideration; that is, the idea which
causes us to doubt is not clear and distinct. (5) To take an example.
(78:6) Supposing that a man has never reflected, taught by experience
or by any other means, that our senses sometimes deceive us, he will
never doubt whether the sun be greater or less than it appears.
(7) Thus rustics are generally astonished when they hear that the
sun is much larger than the earth. (8) But from reflection on the
deceitfulness of the senses [78a] doubt arises, and if, after
doubting, we acquire a true knowledge of the senses, and how things
at a distance are represented through their instrumentality, doubt
is again removed. 

[79]  (1) Hence we cannot cast doubt on true ideas by the supposition
that there is a deceitful Deity, who leads us astray even in what is
most certain.  (2) We can only hold such an hypothesis so long as we
have no clear and distinct idea - in other words, until we reflect 
the knowledge which we have of the first principle of all things, and
find that which teaches us that God is not a deceiver, and until we
know this with the same certainty as we know from reflecting on the
are equal to two right angles.  (3) But if we have a knowledge of God
equal to that which we have of a triangle, all doubt is removed.
(79:4) In the same way as we can arrive at the said knowledge of a
triangle, though not absolutely sure that there is not some
arch-deceiver leading us astray, so can we come to a like knowledge
of God under the like condition, and when we have attained to it,
it is sufficient, as I said before, to remove every doubt which we can
possess concerning clear and distinct ideas. 

[80]  (1) Thus, if a man proceeded with our investigations in due
order, inquiring first into those things which should first be
inquired into, never passing over a link in the chain of association,
and with knowledge how to define his questions before seeking to
answer them, he will never have any ideas save such as are very
certain, or, in other words, clear and distinct; for doubt is only a
suspension of the spirit concerning some affirmation or negation
which it would pronounce upon unhesitatingly if it were not in
ignorance of something, without which the knowledge of the matter in
hand must needs be imperfect.  (2) We may, therefore, conclude that
doubt always proceeds from want of due order in investigation.

[81]  (1) These are the points I promised to discuss in the first part
of my treatise on method.  (2) However, in order not to omit anything
which can conduce to the knowledge of the understanding and its
faculties, I will add a few words on the subject of memory and
forgetfulness.
   (81:3) The point most worthy of attention is, that memory is
strengthened both with and without the aid of the understanding.
(4) For the more intelligible a thing is, the more easily is it
remembered, and the less intelligible it is, the more easily do we
forget it.  (5) For instance, a number of unconnected words is much
more difficult to remember than the same number in the form of a
narration.