can hypothesize, or at least suppose, that others are under the 
same mistake as ourselves, or can, like us, fall under it.  (4) We can,
I repeat, thus hypothesize so long as we see no impossibility.
(56:5) Thus, when I tell anyone that the earth is not round, &c.,
I merely recall the error which I perhaps made myself, or which I
might have fallen into, and afterwards I hypothesize that the person
to whom I tell it, is still, or may still fall under the same mistake.
(6) This I say, I can feign so long as I do not perceive any
impossibility or necessity; if I truly understood either one or the
other I should not be able to feign, and I should be reduced to saying
that I had made the attempt.

[57]  (1) It remains for us to consider hypotheses made in problems,
which sometimes involve impossibilities.  (2) For instance, when we
say - let us assume that this burning candle is not burning, or,
let us assume that it burns in some imaginary space, or where there
are no physical objects.  (3) Such assumptions are freely made,
though the last is clearly seen to be impossible.  (4) But, though
this be so, there is no fiction in the case.  (57:5) For, in the first
case, I have merely recalled to memory, [x] another candle not
burning, or conceived the candle before me as without a flame, and
then I understand as applying to the latter, leaving its flame out
of the question, all that I think of the former.  (6) In the second
case, I have merely to abstract my thoughts from the objects
surrounding the candle, for the mind to devote itself to the
contemplation of the candle singly looked at in itself only; I can
then draw the conclusion that the candle contains in itself no
causes for its own destruction, so that if there were no physical
objects the candle, and even the flame, would remain unchangeable,
and so on.  (7) Thus there is here no fiction, but, [y] true and
bare assertions. 

[58] (1) Let us now pass on to the fictions concerned with essences
only, or with some reality or existence simultaneously.  (2) Of
these we must specially observe that in proportion as the mind's
understanding is smaller, and its experience multiplex, so will its
power of coining fictions be larger, whereas as its understanding
increases, its capacity for entertaining fictitious ideas becomes
less.  (58:3) For instance, in the same way as we are unable, while
we are thinking, to feign that we are thinking or not thinking, so,
also, when we know the nature of body we cannot imagine an infinite
fly; or, when we know the nature of the soul, [z] we cannot imagine
it as square, though anything may be expressed verbally.  (4) But,
as we said above, the less men know of nature the more easily can
they coin fictitious ideas, such as trees speaking, men instantly
changed into stones, or into fountains, ghosts appearing in mirrors,
something issuing from nothing, even gods changed into beasts and men
and infinite other absurdities of the same kind. 

[59] (1) Some persons think, perhaps, that fiction is limited by
fiction, and not by understanding; in other words, after I have
formed some fictitious idea, and have affirmed of my own free will
that it exists under a certain form in nature, I am thereby
precluded from thinking of it under any other form.  (2) For
instance, when I have feigned (to repeat their argument) that the
nature of body is of a certain kind, and have of my own free will
desired to convince myself that it actually exists under this
form, I am no longer able to hypothesize that a fly, for example,
is infinite; so, when I have hypothesized the essence of the soul,
I am not able to think of it as square, &c. 

[60] (1) But these arguments demand further inquiry. (2) First,
their upholders must either grant or deny that we can understand
anything. If they grant it, then necessarily the same must be
said of understanding, as is said of fiction. (3) If they deny
it, let us, who know that we do know something, see what they
mean.  (4) They assert that the soul can be conscious of, and
perceive in a variety of ways, not itself nor things which
exist, but only things which are neither in itself nor anywhere
else, in other words, that the soul can, by its unaided power,
create sensations or ideas unconnected with things.  (5) In fact,
they regard the soul as a sort of god.  (60:6) Further, they assert
that we or our soul have such freedom that we can constrain
ourselves, or our soul, or even our soul's freedom.  (7) For,
after it has formed a fictitious idea, and has given its assent
thereto, it cannot think or feign it in any other manner, but is
constrained by the first fictitious idea to keep all its other
thoughts in harmony therewith.  (8) Our opponents are thus driven
to admit, in support of their fiction, the absurdities which I
have just enumerated; and which are not worthy of rational
refutation. 

[61]  (1) While leaving such persons in their error, we will take
care to derive from our argument with them a truth serviceable for
our purpose, namely, [61a] that the mind, in paying attention to
a thing hypothetical or false, so as to meditate upon it and
understand it, and derive the proper conclusions in due order
therefrom, will readily discover its falsity; and if the thing
hypothetical be in its nature true, and the mind pays attention 
to it, so as to understand it, and deduce the truths which are
derivable from it, the mind will proceed with an uninterrupted
series of apt conclusions; in the same way as it would at once
discover (as we showed just now) the absurdity of a false
hypothesis, and of the conclusions drawn from it. 

[62]  (1) We need, therefore, be in no fear of forming hypotheses,
so long as we have a clear and distinct perception of what is
involved.  (2) For, if we were to assert, haply, that men are
suddenly turned into beasts, the statement would be extremely
general, so general that there would be no conception, that is,