Spinoza moves first to a definition of idea to focus on what a
mind does - it is a thinking thing, a mode, and its modal expression is
the formation of ideas. The idea is formed as a concept of the mind as
by the mind's action or power, not as a passive impression by an
object. If the mind were passive to objects, the attribute of
thinking would simply be a subset of the attribute of extending. To be
separate but equal within substance, both attributes need to
independently express the essence of substance.
This
separation between object and idea seems foreign. Spinoza is not
completely separating idea from object, because both idea and object are
deeply connected through the mode itself that gives rise to them. The
mode itself which expresses itself through either its extending aspect
or its thinking aspect.
An example from childhood might
make this "separate but equal but still the same in reality" more
clear. Occasionally children discuss the relative merits of seeing
versus hearing. Each aspect of gathering sensory data has its own
characteristics. Neither informs the other in a dominant way. They are
separate but equal in gathering information differently about the same
underlying reality.
The emphasis on action or power
of the mind not only maintaining the unitary operation of God's
expressive force within both attributes of thinking (IID3) and
extending (IID1) but also holds significant implications for blessedness
as the Ethics unfolds.
Given this unitary structure of
Spinoza (in contrast to Descartes' dualism), consider the contrast to
II.D1. There, the body is a mode under the aspect of extending. Here,
the mind is similarly a mode under the aspect of thinking. So, if the
mind forms ideas under the fact that it is a thinking thing, what does
the body do under the fact that it is an extending thing? It attempts to
persevere and extend its existence.
Thinking is different
than Knowing in the same way as extending is different than Being or
Existing. Thinking and extending are simply perspectival attributes and
mode-based. Knowing and Being are conceptual and substance-based. This
distinction of conceiving versus perceiving has held since ID4. The mind
referred to here is not the operation of individual human minds, but
mind as modal expression of the attribute of thinking.
Per ideam intelligo mentis conceptum quem mens format propterea quod res est cogitans.
Explicatio: Dico potius conceptum quam perceptionem quia perceptionis nomen indicare videtur mentem ab objecto pati. At conceptus actionem mentis exprimere videtur.
Translated as,
By idea, I understand a concept of the mind which the mind forms on account of the fact that the thing [mind] is [a] thinking [thing].
Explanation: I say concept rather than a perception because the name perception seems to indicate that the mind is acted on by an object. But concept seems to express an action of the mind.