Unformatted text preview: be the adequate cause of any of these states, the affect in question is
what I call an ‘action’; otherwise it is a ‘passion’.
Postulate 1: A human body can be in many states in which its power of acting is increased
or lessened, and also in others which render its power of acting neither greater nor less.
This postulate or axiom rests on postulate 1 and L5 and L7 ·in the physical interlude·
Postulate 2: While a human body undergoes many changes it can retain impressions or
traces of objects ·that it has interacted with· (on this see postulate 5 in Part II); and
consequently it can retain the same images of things. (For the definition of ‘image’ see the
note on II17.) 57
1: Our mind ·actively· does certain things and ·passively· undergoes other things;
specifically, in having adequate ideas it necessarily does certain things, and in
having inadequate ideas it necessarily undergoes other things.
[The demonstration of this is needlessly difficult. It rests on understanding ‘Idea x is
adequate in (or: relative to) mind y’ to mean ‘Idea x occurs in mind y, and its causes
also occur wholly in y’. That easily yields the result that a mind is active with respect
to its adequate ideas and at least partly passive with respect to its inadequate ideas.
Spinoza’s version does bring out the important point that every idea is adequate
relative to God’s mind.]
Corollary: A mind is more liable to passions [= ‘passive states’] the more it has
inadequate ideas, and more active the more it has adequate ideas.
2: A body cannot cause a mind to think, and a mind cannot cause a body to be in
motion or at rest or in any other state (if there are any others).
All modes of thinking have for a cause God-considered-as-thinking and not Godconsidered-as-having-A where A is any other attribute (by II6). So what causes a
mind to think is some detail of the realm of thought and not of extension, that is (by
D1), it is not the body. This was the first point. [The argument for the second half
of 2 is strictly analogous to that: the motion and rest of a body must be caused by
God-considered-as-extended, and thus not caused by the mind.]
Note on 2: These things are more clearly understood from what I said in the note on II7,
namely that a mind and the ·corresponding· body are one and the same thing conceived
under different attributes. The result is that there is just one natural order or connection of
events, whether Nature is conceived under this attribute or that; so the order of actions
and passions of our body naturally corresponds with the order of actions and passions of
our mind. This is also evident from my way of demonstrating II12.
But although there is no real room for doubt about these points, I don’t expect people
to be willing to consider them fairly unless I confirm them by experience. ·That is because·
men are so firmly convinced that the body moves and stops moving at the mind’s
command, and that it does a great many things that depend only on the mind’s will and its
skill in thinking. ·This firm conviction is unreasonable, because· no-one has yet determined
what a body can do - that is, experience hasn’t yet taught anyone what a body can do
Ÿpurely through the laws of physics and what ·if anything· a body can do only if it is Ÿacted
on by a mind. For no-one has yet come to know the structure of the ·human· body so
accurately that he could explain all its functions - not to mention that many things are
observed in the lower animals that far surpass human ingenuity, and that sleepwalkers do a
great many things in their sleep that they wouldn’t venture to do when awake. This shows
well enough that the body itself, simply from the laws of its own ·physical· nature, can do
many things that its mind is amazed by!
Again, no-one knows how the mind moves the body, or in how many ways it can
make it move, or how fast. So when men say that this or that action of the body ‘arises
from the mind, which rules over the body’, they don’t know what they are saying. All they
communicate in their fine-sounding words is an admission that Ÿthey are ignorant of the
true cause of that action and that Ÿthey do not wonder at it! 58
But they will say that - whether or not they know how the mind moves the body they still know by experience [i] that it does so, i.e. that if a human mind couldn’t think the
·corresponding· body couldn’t act. And then they know by experience [ii] that only the
mind can decide whether a man shall speak or be silent, and other such things that they
therefore believe depend on the mind’s decision.
[i] As far as the first ·objection· is concerned, I reply:
Doesn’t experience also teach that if a body is inactive the ·corresponding· mind
can’t think? For when a body is at rest in sleep, the mind at the same time remains
senseless, with no power of thinking such as it has when awake. And I think
everyone has found from experience that the mind isn’t always equally capable of
thinking of the same object, and that the man’s ability to think about this or that
object depends on how capable the body is of having the image of the object.
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