what standard of truth can there be that is clearer and more certain than a true idea?
Indeed, just as light makes manifest both itself and darkness, so truth is the standard both
of itself and falsity.
I think I have thus given an answer to those questions which can be stated as
follows: If a true idea is distinguished from a false one only inasmuch as it is said to
correspond with that of which it is an idea, then a true idea has no more reality or
perfection than a false one (since they are distinguished only by an extrinsic character-
istic) and consequently neither is a man who has true ideas superior to one who has
only false ideas. Secondly, how do we come to have false ideas? And finally, how can
one know for certain that one has ideas which correspond with that of which they are
ideas? I have now given an answer, I repeat, to these problems. As regards the differ-
ence between a true and a false idea, it is clear from Pr. 35, II that the former is to the
latter as being to non-being. The causes of falsity I have quite clearly shown from
Propositions 19 to 35 with the latter’s Scholium, from which it is likewise obvious
what is the difference between a man who has true ideas and one who has only false
ideas. As to the last question, how can a man know that he has an idea which corre-
sponds to that of which it is an idea, I have just shown, with abundant clarity, that this
arises from the fact that he does have an idea that corresponds to that of which it is an
idea; that is, truth is its own standard. Furthermore, the human mind, insofar as it
perceives things truly, is part of the infinite intellect of God (Cor. Pr. 11, II), and thus it
is as inevitable that the clear and distinct ideas of the mind are true as that God’s ideas
are true.
PROPOSITION 44:It is not in the nature of reason to regard things as contingent, but
as necessary.
Proof: It is in the nature of reason to perceive things truly (Pr. 41, II), to wit (Ax. 6, I),
as they are in themselves; that is (Pr. 29, I), not as contingent, but as necessary.
Corollary 1: Hence it follows that it solely results from imagination [imaginatio]
that we regard things, both in respect of the past and of the future, as contingent.
Scholium: I shall explain briefly how this comes about. We have shown above
(Pr. 17, II and Cor.) that although things may not exist, the mind nevertheless always
imagines them as present unless causes arise which exclude their present existence.
Further, we have shown (Pr. 18, II) that if the human body has once been affected by two
external bodies at the same time, when the mind later imagines one of them, it will
straightway call the other to mind as well; that is, it will regard both as present to it unless
other causes arise which exclude their present existence. Furthermore, nobody doubts
that time, too, is a product of the imagination, and arises from the fact that we see some
bodies move more slowly than others, or more quickly, or with equal speed. Let us there-
fore suppose that yesterday a boy saw Peter first of all in the morning, Paul at noon, and
Simon in the evening, and that today he again sees Peter in the morning. From Pr. 18, II
it is clear that as soon as he sees the morning light, forthwith he will imagine the sun as
traversing the same tract of sky as on the previous day, that is, he will imagine a whole
day, and he will imagine Peter together with morning, Paul with midday, and Simon with
evening; that is, he will imagine the existence of Paul and Simon with reference to future
time. On the other hand, on seeing Simon in the evening he will refer Paul and Peter to
time past by imagining them along with time past. This train of events will be the more
consistent the more frequently he sees them in that order. If it should at some time occur
that on another evening he sees James instead of Simon, then the following morning
he will imagine along with evening now Simon, now James, but not both together.