fact, that true knowledge consists in knowing things through their
primary causes, wherein it is totally different from false knowledge,
as I have just explained it: for thought is said to be true, if
it involves subjectively the essence of any principle which has no
cause, and is known through itself and in itself.

[71] (1) Wherefore the reality (forma) of true thought must exist
in the thought itself, without reference to other thoughts; it does
not acknowledge the object as its cause, but must depend on the
actual power and nature of the understanding. (2) For, if we
suppose that the understanding has perceived some new entity which
has never existed, as some conceive the understanding of God before
He created thing (a perception which certainly could not arise
any object), and has legitimately deduced other thoughts from said
perception, all such thoughts would be true, without being
determined by any external object; they would depend solely on the
power and nature of the understanding. (71:3) Thus, that which
constitutes the reality of a true thought must be sought in the
thought itself, and deduced from the nature of the understanding.

[72] (1) In order to pursue our investigation, let us confront
ourselves with some true idea, whose object we know for
certain to be dependent on our power of thinking, and to have
nothing corresponding to it in nature. (2) With an idea of this
kind before us, we shall, as appears from what has just been said,
be more easily able to carry on the research we have in view.
(72:3) For instance, in order to form the conception of a sphere,
I invent a cause at my pleasure - namely, a semicircle revolving
round its center, and thus producing a sphere. (4) This is
indisputably a true idea; and, although we know that no sphere in