allows us to do so, though the nature of things does not.  (5) While
we remain unaware of this fact, we may easily mistake falsehood for
truth.

[90] (1) Let us also beware of another great cause of confusion,
which prevents the understanding from reflecting on itself.
(2) Sometimes, while making no distinction between the imagination
and the intellect, we think that what we more readily imagine is
clearer to us; and also we think that what we imagine we understand.
(3) Thus, we put first that which should be last: the true order of
progression is reversed, and no legitimate conclusion is drawn. 

[91]  [91e] (1) Now, in order at length to pass on to the second
part of this method, I shall first set forth the object aimed at,
and next the means for its attainment.  (2) The object aimed at
is the acquisition of clear and distinct ideas, such as are
produced by the pure intellect, and not by chance physical motions.
(3) In order that all ideas may be reduced to unity, we shall
endeavor so to associate and arrange them that our mind may, as far
as possible, reflect subjectively the reality of nature, both as
a whole and as parts. 

[92] (1) As for the first point, it is necessary (as we have said)
for our purpose that everything should be conceived, either solely
through its essence, or through its proximate cause.  (2) If the
thing be self-existent, or, as is commonly said, the cause of
itself, it must be understood through its essence only; if it be
not self-existent, but requires a cause for its existence, it must
be understood through its proximate cause.  (3) For, in reality,
the knowledge, [92f] of an effect is nothing else than the
acquisition of more perfect knowledge of its cause. 

[93] (1) Therefore, we may never, while we are concerned with
inquiries into actual things, draw any conclusion from
abstractions; we shall be extremely careful not to confound that
which is only in the understanding with that which is in the
thing itself. (2) The best basis for drawing a conclusion will
be either some particular affirmative essence, or a true and
legitimate definition.  (93:3) For the understanding cannot descend
from universal axioms by themselves to particular things, since
axioms are of infinite extent, and do not determine the
understanding to contemplate one particular thing more than
another. 

[94] (1) Thus the true method of discovery is to form thoughts
from some given definition.  (2) This process will be the
more fruitful and easy in proportion as the thing given be
better defined.  (3) Wherefore, the cardinal point of all this
second part of method consists in the knowledge of the conditions
of good definition, and the means of finding them.  (4) I will
first treat of the conditions of definition.

[95]  (1) A definition, if it is to be called perfect, must
explain the inmost essence of a thing, and must take care not
to substitute for this any of its properties.  (2) In order
to illustrate my meaning, without taking an example which
would seem to show a desire to expose other people's errors,
I will choose the case of something abstract, the definition
of which is of little moment.  (95:3) Such is a circle.  (4) If
a circle be defined as a figure, such that all straight lines
drawn from the center to the circumference are equal, every
one can see that such a definition does not in the least
explain the essence of a circle, but solely one of its
properties.  (5) Though, as I have said, this is of no
importance in the case of figures and other abstractions,
it is of great importance in the case of physical beings
and realities: for the properties of things are not understood
so long as their essences are unknown. (6) If the latter be
passed over, there is necessarily a perversion of the
succession of ideas which should reflect the succession of
nature, and we go far astray from our object.

[96]  In order to be free from this fault, the following rules
should be observed in definition:-
I.  (1) If the thing in question be created, the definition
   must (as we have said) comprehend the proximate cause.
   (2) For instance, a circle should, according to this rule,
   be defined as follows: the figure described by any line
   whereof one end is fixed and the other free.  (3) This
   definition clearly comprehends the proximate cause.
II.  (4) A conception or definition of a thing should be such
   that all the properties of that thing, in so far as it is
   considered by itself, and not in conjunction with other
   things, can be deduced from it, as may be seen in the
   definition given of a circle: for from that it clearly follows
   that all straight lines drawn from the center to the
   circumference are equal.  (5) That this is a necessary
   characteristic of a definition is so clear to anyone, who
   reflects on the matter, that there is no need to spend time
   in proving it, or in showing that, owing to this second
   condition, every definition should be affirmative.  (6) I
   speak of intellectual affirmation, giving little thought to
   verbal affirmations which, owing to the poverty of language,
   must sometimes, perhaps, be expressed negatively, though
   the idea contained is affirmative.

[97]  The rules for the definition of an uncreated thing
are as follows:--
I.  The exclusion of all idea of cause - that is, the thing
   must not need explanation by Anything outside itself.