Benedict de Spinoza, THE ETHICS
(Ethica Ordine Geometrico Demonstrata)

Translated by R. H. M. Elwes




Part II:  ON THE NATURE AND ORIGIN OF THE MIND



PREFACE I now pass on to explaining the results, which must
necessarily follow from the essence of  God, or of the eternal
and infinite being; not, indeed, all of them (for we proved in
Part i.,  Prop. xvi., that an infinite number must follow in an
infinite number of ways), but only  those which are able to lead
us, as it were by the hand, to the knowledge of the human  mind
and its highest blessedness.

DEFINITIONS I.  By 'body' I mean a mode which expresses in a
certain determinate manner the essence  of God, in so far as he
is considered as an extended thing.  (See Pt. i., Prop. xxv.
Cor.)

II.  I consider as belonging to the essence of a thing that,
which being given, the thing is  necessarily given also, and,
which being removed, the thing is necessarily removed also;  in
other words, that without which the thing, and which itself
without the thing, can neither  be nor be conceived.

III. By 'idea,' I mean the mental conception which is formed by
the mind as a thinking  thing.

>>>>>Explanation--I say 'conception' rather than perception,
because the word perception  seems to imply that the mind is
passive in respect to the object; whereas conception seems  to
express an activity of the mind.

IV.  By 'an adequate idea,' I mean an idea which, in so far as
it is considered in itself,  without relation to the object, has
all the properties or intrinsic marks of a true idea.

>>>>>Explanation--I say 'intrinsic,' in order to exclude that
mark which is extrinsic,  namely, the agreement between the idea
and its object (ideatum).

V.  'Duration' is the indefinite continuance of existing.

>>>>>Explanation--I say 'indefinite,' because it cannot be
determined through the  existence itself of the existing thing,
or by its efficient cause, which necessarily gives the  existence
of the thing, but does not take it away.

VI.  'Reality' and 'perfection' I use as synonymous terms.

VII.  By 'particular things,' I mean things which are finite and
have a conditioned  existence; but if several individual things
concur in one action, so as to be all  simultaneously the effect
of one cause, I consider them all, so far, as one particular 
thing.

 AXIOMS  I.  The essence of man does not involve necessary
existence, that is, it may, in the order of  nature, come to pass
that this or that man does or does not exist.

II.  Man thinks.

III.  Modes of thinking, such as love, desire, or any other of
the passions, do not take place,  unless there be in the same
individual an idea of the thing loved, desired, &c.  But the idea 
can exist without the presence of any other mode of thinking.

IV.  We perceive that a certain body is affected in many ways.

V.  We feel and perceive no particular things, save bodies and
modes of thought.

N.B.  The Postulates are given after the conclusion of Prop.
xiii.

 PROPOSITIONS  I.  Thought is an attribute of God, or God is a
thinking thing.

>>>>>Proof--Particular thoughts, or this and that thought, are
modes which, in a certain  conditioned manner, express the nature
of God (Pt. i., Prop. xxv., Cor.).  God therefore  possesses the
attribute (Pt. i., Def. v.) of which the concept is involved in
all particular  thoughts, which latter are conceived thereby. 
Thought, therefore, is one of the infinite  attributes of God,
which express God's eternal and infinite essence (Pt. i., Def.
vi.).  In  other words, God is a thinking thing.  Q.E.D.

*****Note--This proposition is also evident from the fact, that
we are able to conceive  an infinite thinking being.  For, in
proportion as a thinking being is conceived as thinking  more
thoughts, so is it conceived as containing more reality or
perfection.  Therefore a  being, which can think an infinite
number of things in an infinite number of ways, is, 
necessarily, in respect of thinking, infinite.  As, therefore,
from the consideration of  thought alone, we conceive an infinite
being, thought is necessarily (Pt. i., Deff. iv. and vi.)  one of
the infinite attributes of God, as we were desirous of showing.

II.  Extension is an attribute of God, or God is an extended
thing.

>>>>>Proof--The proof of this proposition is similar to that of
the last.

III.  In God there is necessarily the idea not only of his
essence, but also of all things which  necessarily follow from
his essence.

>>>>>Proof--God (by the first Prop. of this Part) can think an
infinite number of things in  infinite ways, or (what is the same
thing, by Prop. xvi., Part i.) can form the idea of his  essence,
and of all things which necessarily follow therefrom.  Now all
that is in the power  of God necessarily is (Pt. i., Prop.
xxxv.).  Therefore, such an idea as we are considering 
necessarily is, and in God alone.  Q.E.D.  (Part i., Prop. xv.)

*****Note--The multitude understand by the power of God the free
will of God, and the  right over all things that exist, which
latter are accordingly generally considered as  contingent.  For
it is said that God has the power to destroy all things, and to
reduce them  to nothing.  Further, the power of God is very often
likened to the power of kings.  But  this doctrine we have
refuted (Pt. i., Prop. xxxii., Cors. i. and ii.), and we have
shown  (Part i., Prop. xvi.) that God acts by the same necessity,
as that by which he understands  himself; in other words, as it
follows from the necessity of the divine nature (as all admit), 
that God understands himself, so also does it follow by the same
necessity, that God  performs infinite acts in infinite ways.  We
further showed (Part i., Prop. xxxiv.), that  God's power is
identical with God's essence in action; therefore it is as
impossible for us  to conceive God as not acting, as to conceive
him as non-existent.  If we might pursue  the subject further, I
could point out, that the power which is commonly attributed to
God  is not only human (as showing that God is conceived by the
multitude as a man, or in the  likeness of a man), but involves a
negation of power.  However, I am unwilling to go over  the same
ground so often.  I would only beg the reader again and again, to
turn over  frequently in his mind what I have said in Part i.
from Prop. xvi. to the end.  No one will  be able to follow my
meaning, unless he is scrupulously careful not to confound the
power  of God with the human power and right of kings.

IV.  The idea of God, from which an infinite number of things
follow in infinite ways, can  only be one.

>>>>>Proof--Infinite intellect comprehends nothing save the
attributes of God and his  modifications (Part i., Prop. xxx.). 
Now God is one (Part i., Prop. xiv., Cor.).  Therefore  the idea
of God, wherefrom an infinite number of things follow in infinite
ways, can only  be one.  Q.E.D.

V.  The actual being of ideas owns God as its cause, only in so
far as he is considered as a  thinking thing, not in so far as he
is unfolded in any other attribute; that is, the ideas both  of
the attributes of God and of particular things do not own as
their efficient cause their  objects (ideata) or the things
perceived, but God himself in so far as he is a thinking thing.

>>>>>Proof--This proposition is evident from Prop. iii. of this
Part.  We there drew the  conclusion, that God can form the idea
of his essence, and of all things which follow  necessarily
therefrom, solely because he is a thinking thing, and not because
he is the  object of his own idea.  Wherefore the actual being of
ideas owns for cause God, in so far  as he is a thinking thing. 
It may be differently proved as follows:  the actual being of
ideas  is (obviously) a mode of thought, that is (Part i., Prop.
xxv., Cor.) a mode which expresses  in a certain manner the
nature of God, in so far as he is a thinking thing, and therefore 
(Part i., Prop. x.) involves the conception of no other attribute
of God, and consequently  (by Part i., Ax. iv.) is not the effect
of any attribute save thought.  Therefore the actual  being of
ideas owns God as its cause, in so far as he is considered as a
thinking thing, &c.   Q.E.D.

VI.  The modes of any given attribute are caused by God, in so
far as he is considered  through the attribute of which they are
modes, and not in so far as he is considered through  any other
attribute.

>>>>>Proof--Each attribute is conceived through itself, without
any other part (Part i.,  Prop. x.); wherefore the modes of each
attribute involve the conception of that attribute,  but not of
any other.  Thus (Part i., Ax. iv.) they are caused by God, only
in so far as he  is considered through the attribute whose modes
they are, and not in so far as he is  considered through any
other.  Q.E.D.

<<<<>>>>Proof--This proposition is evident from Part i., Ax. iv. 
For the idea of everything  that is caused depends on a
knowledge of the cause, whereof it is an effect.

<<<<>>>>Proof--This proposition is evident from the last; it is
understood more clearly from  the preceding note.

<<<<>>>>Proof--The idea of an individual thing actually existing is
an individual mode of  thinking, and is distinct from other modes
(by the Cor. and Note to Prop. viii. of this part);  thus (by
Prop. vi. of this part) it is caused by God, in so far only as he
is a thinking thing.   But not (by Prop. xxviii. of Part i.) in
so far as he is a thing thinking absolutely, only in so  far as
he is considered as affected by another mode of thinking; and he
is the cause of this  latter, as being affected by a third, and
so on to infinity.  Now, the order and connection  of ideas is
(by Prop. vii. of this book) the same as the order and connection
of causes.   Therefore of a given individual idea another
individual idea, or God, in so far as he is  considered as
modified by that idea, is the cause; and of this second idea God
is the  cause, in so far as he is affected by another idea, and
so on to infinity.  Q.E.D.

<<<<>>>>Proof--Whatsoever takes place in the object of any idea, its
idea is in God (by  Prop. iii. of this part), not in so far as he
is infinite, but in so far as he is considered as  affected by
another idea of an individual thing (by the last Prop.); but (by
Prop. vii. of  this part) the order and connection of ideas is
the same as the order and connection of  things.  The knowledge,
therefore, of that which takes place in any individual object
will  be in God, in so far only as he has the idea of that
object.  Q.E.D.

X.  The being of substance does not appertain to the essence of
man--in other words,  substance does not constitute the actual
being (forma) of man.

>>>>>Proof--The being of substance involves necessary existence
(Part i., Prop. vii.).   If, therefore, the being of substance
appertains to the essence of man, substance being  granted, man
would necessarily be granted also (II. Def. ii.), and,
consequently, man would  necessarily exist, which is absurd (II.
Ax. i.).  Therefore &c.  Q.E.D.

*****Note--This proposition may also be proved from I.v., in
which it is shown that there  cannot be two substances of the
same nature; for as there may be many men, the being of 
substance is not that which constitutes the actual being of man. 
Again, the proposition is  evident from the other properties of
substance--namely, that substance is in its nature  infinite,
immutable, indivisible, &c., as anyone may see for himself.

<<<<>>>>Proof--The essence of man (by the Cor. of the last Prop.) is
constituted by certain  modes of the attributes of God, namely
(by II. Ax. ii.), by the modes of thinking, of all  which (by II.
Ax. iii.) the idea is prior in nature, and, when the idea is
given, the other  modes (namely, those of which the idea is prior
in nature) must be in the same individual  (by the same Axiom). 
Therefore an idea is the first element constituting the human
mind.   But not the idea of a non-existent thing, for then (II.
viii. Cor.) the idea itself cannot be  said to exist; it must
therefore be the idea of something actually existing.  But not of
an  infinite thing.  For an infinite thing (I. xxi., xxii.), must
always necessarily exist; this would  (by II. Ax. i.) involve an
absurdity.  Therefore the first element, which constitutes the 
actual being of the human mind, is the idea of something actually
existing.  Q.E.D.

<<<<>>>>Proof--Whatsoever comes to pass in the object of any idea,
the knowledge  thereof is necessarily in God (II. ix. Cor.), in
so far as he is considered as affected by  the idea of the said
object, that is (II. xi.), in so far as he constitutes the mind
of anything.   Therefore, whatsoever takes place in the object
constituting the idea of the human mind,  the knowledge thereof
is necessarily in God, in so far as he constitutes the essence of
the  human mind; that is (by II. xi. Cor.) the knowledge of the
said thing will necessarily be  in the mind, in other words the
mind perceives it.

*****Note--This proposition is also evident, and is more clearly
to be understood from  II. vii., which see.

XIII.  The object of the idea constituting the human mind is the
body, in other words a  certain mode of extension which actually
exists, and nothing else.

>>>>>Proof--If indeed the body were not the object of the human
mind, the ideas of the  modifications of the body would not be in
God (II. ix. Cor.) in virtue of his constituting  our mind, but
in virtue of his constituting the mind of something else; that is
(II. xi. Cor.)  the ideas of the modifications of the body would
not be in our mind:  now (by II. Ax. iv.)  we do possess the idea
of the modifications of the body.  Therefore the object of the 
idea constituting the human mind is the body, and the body as it
actually exists (II. xi.).   Further, if there were any other
object of the idea constituting the mind besides body,  then, as
nothing can exist from which some effect does not follow (I.
xxxvi.) there would  necessarily have to be in our mind an idea,
which would be the effect of that other object  (II. xi.); but
(I. Ax. v.) there is no such idea.  Wherefore the object of our
mind is the body  as it exists, and nothing else.  Q.E.D.

*****Note--We thus comprehend, not only that the human mind is
united to the body,  but also the nature of the union between
mind and body.  However, no one will be able  to grasp this
adequately or distinctly, unless he first has adequate knowledge
of the nature  of our body.  The propositions we have advanced
hitherto have been entirely general,  applying not more to men
than to other individual things, all of which, though in
different  degrees, are animated (animata).  For of everything
there is necessarily an idea in God, of  which God is the cause,
in the same way as there is an idea of the human body; thus 
whatever we have asserted of the idea of the human body must
necessarily also be asserted  of the idea of everything else. 
Still, on the other hand, we cannot deny that ideas, like 
objects, differ one from the other, one being more excellent than
another and containing  more reality, just as the object of one
idea is more excellent than the object of another idea,  and
contains more reality.

Wherefore, in order to determine, wherein the human mind differs
from other things, and  wherein it surpasses them, it is
necessary for us to know the nature of its object, that is,  of
the human body.  What this nature is, I am not able here to
explain, nor is it necessary  for the proof of what I advance,
that I should do so.  I will only say generally, that in 
proportion as any given body is more fitted than others for doing
many actions or receiving  many impressions at once, so also is
the mind, of which it is the object, more fitted than  others for
forming many simultaneous perceptions; and the more the actions
of the body  depend on itself alone, and the fewer other bodies
concur with it in action, the more fitted  is the mind of which
it is the object for distinct comprehension.  We may thus
recognize  the superiority of one mind over others, and may
further see the cause, why we have only a  very confused
knowledge of our body, and also many kindred questions, which I
will, in  the following propositions, deduce from what has been
advanced.  Wherefore I have  thought it worth while to explain
and prove more strictly my present statements.  In order  to do
so, I must premise a few propositions concerning the nature of
bodies.

---Axiom I.  All bodies are either in motion or at rest.

---Axiom II.  Every body is moved sometimes more slowly,
sometimes more quickly.

Lemma I.  Bodies are distinguished from one another in respect of
motion and rest,  quickness and slowness, and not in respect of
substance.

>>>>>Proof--The first part of this proposition is, I take it,
self-evident.  That bodies are  not distinguished in respect of
substance, is plain both from I. v. and I. viii.  It is brought 
out still more clearly from I. xv., Note.

Lemma II.  All bodies agree in certain respects.

>>>>>Proof--All bodies agree in the fact, that they involve the
conception of one and the  same attribute (II., Def. i.). 
Further, in the fact that they may be moved less or more 
quickly, and may be absolutely in motion or at rest.

Lemma III.  A body in motion or at rest must be determined to
motion or rest by another  body, which other body has been
determined to motion or rest by a third body, and that  third
again by a fourth, and so on to infinity.

>>>>>Proof--Bodies are individual things (II., Def. i.), which
(Lemma i.) are distinguished  one from the other in respect to
motion and rest; thus (I. xxviii.) each must necessarily be 
determined to motion or rest by another individual thing, namely
(II. vi.) by another body,  which other body is also (Ax. i.) in
motion or at rest.  And this body again can only have  been set
in motion or caused to rest by being determined by a third body
to motion or rest.   This third body again by a fourth, and so on
to infinity.  Q.E.D.

<<<<>>>>Proof--Bodies (Lemma i.) are not distinguished in respect of
substance:  that which  constitutes the actuality (formam) of an
individual consists (by the last Def.) in a union of  bodies; but
this union, although there is a continual change of bodies, will
(by our  hypothesis) be maintained; the individual, therefore,
will retain its nature as before, both in  respect of substance
and in respect of mode.  Q.E.D.

Lemma V.  If the parts composing an individual become greater or
less, but in such  proportion, that they all preserve the same
mutual relations of motion and rest, the  individual will still
preserve its original nature, and its actuality will not be
changed.

>>>>>Proof--The same as for the last Lemma.

Lemma VI.  If certain bodies composing an individual be compelled
to change the motion,  which they have in one direction, for
motion in another direction, but in such a manner,  that they be
able to continue their motions and their mutual communication in
the same  relations as before, the individual will retain its own
nature without any change of its  actuality.

>>>>>Proof--This proposition is self-evident, for the individual
is supposed to retain all  that, which, in its definition, we
spoke of as its actual being.

Lemma VII.  Furthermore, the individual thus composed preserves
its nature, whether it  be, as a whole, in motion or at rest,
whether it be moved in this or that direction; so long  as each
part retains its motion, and preserves its communication with
other parts as  before.

>>>>>Proof--This proposition is evident from the definition of an
individual prefixed to  Lemma iv.

*****Note--We thus see, how a composite individual may be
affected in many different  ways, and preserve its nature
notwithstanding.  Thus far we have conceived an individual  as
composed of bodies only distinguished one from the other in
respect of motion and  rest, speed and slowness; that is, of
bodies of the most simple character.  If, however, we  now
conceive another individual composed of several individuals of
diverse natures, we  shall find that the number of ways in which
it can be affected, without losing its nature, will  be greatly
multiplied.  Each of its parts would consist of several bodies,
and therefore (by  Lemma vi.) each part would admit, without
change to its nature, of quicker or slower  motion, and would
consequently be able to transmit its motions more quickly or more
 slowly to the remaining parts.  If we further conceive a third
kind of individuals composed  of individuals of this second kind,
we shall find that they may be affected in a still greater 
number of ways without changing their actuality.  We may easily
proceed thus to infinity,  and conceive the whole of nature as
one individual, whose parts, that is, all bodies, vary in 
infinite ways, without any change in the individual as a whole. 
I should feel bound to  explain and demonstrate this point at
more length, if I were writing a special treatise on  body.  But
I have already said that such is not my object; I have only
touched on the  question, because it enables me to prove easily
that which I have in view.

POSTULATES I.  The human body is composed of a number of
individual parts, of diverse nature, each  one of which is in
itself extremely complex.

II.  Of the individual parts composing the human body some are
fluid, some soft, some  hard.

III.  The individual parts composing the human body, and
consequently the human body  itself, are affected in a variety of
ways by external bodies.

IV.  The human body stands in need for its preservation of a
number of other bodies, by  which it is continually, so to speak,
regenerated.

V.  When the fluid part of the human body is determined by an
external body to impinge  often on another soft part, it changes
the surface of the latter, and, as it were, leaves the 
impression thereupon of the external body which impels it.

VI.  The human body can move external bodies, and arrange them in
a variety of ways.

PROPOSITIONS XIV.  The human mind is capable of perceiving a
great number of things, and is so in   proportion as its body is
capable of receiving a great number of impressions.

>>>>>Proof--The human body (by Post. iii. and vi.) is affected in
very many ways by  external bodies, and is capable in very many
ways of affecting external bodies.  But (II.xii.)  the human mind
must perceive all that takes place in the human body; the human
mind is,  therefore, capable of perceiving a great number of
things, and is so in proportion, &c.   Q.E.D.

XV.  The idea, which constitutes the actual being of the human
mind, is not simple, but  compounded of a great number of ideas.

>>>>>Proof--The idea constituting the actual being of the human
mind is the idea of the  body (II. xiii.), which (Post. i.) is
composed of a great number of complex individual  parts.  But
there is necessarily in God the idea of each individual part
whereof the body is  composed (II. viii. Cor.); therefore (II.
vii.), the idea of the human body is composed of  each of these
numerous ideas of its component parts.  Q.E.D.

XVI.  The idea of every mode, in which the human body is
affected by external bodies,  must involve the nature of the
human body, and also the nature of the external body.

>>>>>Proof--All the modes, in which any given body is affected,
follow from the nature  of the body affected, and also from the
nature of the affecting body (by Ax. i., after the  Cor. of Lemma
iii.), wherefore their idea is also necessarily (by I, Ax. iv.)
involves the  nature of both bodies; therefore, the idea of every
mode, in which the human body is  affected by external bodies,
involves the nature of the human body and of the external  body. 
Q.E.D.

<<<<>>>>Proof--This proposition is self-evident, for so long as the
human body continues to  be thus affected, so long will the human
mind (II. xii.) regard this modification of the body  --that is
(by the last Prop.), it will have the idea of the mode as
actually existing, and this  idea involves the nature of the
external body; therefore the mind (by II. xvi., Cor. i.) will 
regard the external body as actually existing, until it is
affected, &c.  Q.E.D.

<<<<>>>>Proof--When external bodies determine the fluid parts of the
human body, so that  they often impinge on the softer parts, they
change the surface of the last named (Post. v);  hence (Ax. ii.,
after the Cor. of Lemma iii.) they are refracted therefrom in a
different  manner from that which they followed before such
change; and, further, when afterwards  they impinge on the new
surfaces by their own spontaneous movement, they will be 
refracted in the same manner, as though they had been impelled
towards those surfaces by  external bodies; consequently, they
will, while they continue to be thus refracted, affect the  human
body in the same manner, whereof the mind (II. xii.) will again
take cognizance  --that is (II. xvii.), the mind will again
regard the external body as present, and will do so,  as often as
the fluid parts of the human body impinge on the aforesaid
surfaces by their  own spontaneous motion.  Wherefore, although
the external bodies, by which the human  body has once been
affected, be no longer in existence, the mind will nevertheless
regard  them as present, as often as this action of the body is
repeated.  Q.E.D.

*****Note--We thus see how it comes about, as is often the case,
that we regard as  present many things which are not.  It is
possible that the same result may be brought about  by other
causes; but I think it suffices for me here to have indicated one
possible  explanation, just as well as if I had pointed out the
true cause.  Indeed, I do not think I  am very far from the
truth, for all my assumptions are based on postulates, which
rest,  almost without exception, on experience, that cannot be
controverted by those who have  shown, as we have, that the human
body, as we feel it, exists (Cor. after II. xiii.).   Furthermore
(II. vii. Cor., II. xvi. Cor. ii.), we clearly understand what is
the difference  between the idea, say, of Peter, which
constitutes the essence of Peter's mind, and the  idea of the
said Peter, which is in another man, say, Paul.  The former
directly answers to  the essence of Peter's own body, and only 
implies existence so long as Peter exists; the  latter indicates
rather the disposition of Paul's body than the nature of Peter,
and,  therefore, while this disposition of Paul's body lasts,
Paul's mind will regard Peter as  present to itself, even though
he no longer exists.  Further, to retain the usual phraseology, 
the modifications of the human body, of which the ideas represent
external bodies as  present to us, we will call the images of
things, though they do not recall the figure of  things.  When
the mind regards bodies in this fashion, we say that it imagines. 
I will here  draw attention to the fact, in order to indicate
where error lies, that the imaginations of the  mind, looked at
in themselves, do not contain error.  The mind does not err in
the mere act  of imagining, but only in so far as it is regarded
as being without the idea, which excludes  the existence of such
things as it imagines to be present to it.  If the mind, while
imagining  non-existent things as present to it, is at the same
time conscious that they do not really  exist, this power of
imagination must be set down to the efficacy of its nature, and
not to a  fault, especially if this faculty of imagination depend
solely on its own nature--that is (I.  Def. vii.), if this
faculty of imagination be free.

XVIII.  If the human body has once been affected by two or more
bodies at the same  time, when the mind afterwards imagines any
of them, it will straightway remember the  others also.

>>>>>Proof--The mind (II. xvii. Cor.) imagines any given body,
because the human body  is affected and disposed by the
impressions from an external body, in the same manner as  it is
affected when certain of its parts are acted on by the said
external body; but (by our  hypothesis) the body was then so
disposed, that the mind imagined two bodies at once;  therefore,
it will also in the second case imagine two bodies at once, and
the mind, when  it imagines one, will straightway remember the
other.  Q.E.D.

*****Note--We now clearly see what 'Memory' is.  It is simply a
certain association of  ideas involving the nature of things
outside the human body, which association arises in the  mind
according to the order and association of the modifications
(affectiones) of the  human body.  I say, first, it is an
association of those ideas only, which involve the nature  of
things outside the human body:  not of ideas which answer to the
nature of the said  things:  ideas of the modifications of the
human body are, strictly speaking (II. xvi.), those  which
involve the nature both of the human body and of external bodies. 
I say, secondly,  that this association arises according to the
order and association of the modifications of  the human body, in
order to distinguish it from that association of ideas, which
arises from  the order of the intellect, whereby the mind
perceives things through their primary causes,  and which is in
all men the same.  And hence we can further clearly understand,
why the  mind from the thought of one thing, should straightway
arrive at the thought of another  thing, which has no similarity
with the first; for instance, from the thought of the word 
'pomum' (an apple), a Roman would straightway arrive at the
thought of the fruit apple,  which has no similitude with the
articulate sound in question, nor anything in common  with it,
except that the body of the man has often been affected by these
two things; that  is, that the man has often heard the word
'pomum,' while he was looking at the fruit;  similarly every man
will go on from one thought to another, according as his habit
has  ordered the images of things in his body.  For a soldier,
for instance, when he sees the  tracks of a horse in sand, will
at once pass from the thought of a horse to the thought of a 
horseman, and thence to the thought of war, &c.; while a
countryman will proceed from  the thought of a horse to the
thought of a plough, a field, &c.  Thus every man will follow 
this or that train of thought, according as he has been in the
habit of conjoining and  associating the mental images of things
in this or that manner.

XIX.  The human mind has no knowledge of the body, and does not
know it to exist, save  through the ideas of the modifications
whereby the body is affected.

>>>>>Proof--The human mind is the very idea or knowledge of the
human body (II. xiii.),  which (II. ix.) is in God, in so far as
he is regarded as affected by another idea of a  particular thing
actually existing:  or, inasmuch as (Post. iv.) the human body
stands in  need of very many bodies whereby it is, as it were,
continually regenerated; and the order  and connection of ideas
is the same as the order and connection of causes (II. vii.);
this  idea will therefore be in God, in so far as he is regarded
as affected by the ideas of very  many particular things.  Thus
God has the idea of the human body, or knows the human  body, in
so far as he is affected by very many other ideas, and not in so
far as he  constitutes the nature of the human mind; that is (by
II. xi. Cor.), the human mind does not  know the human body.  But
the ideas of the modifications of body are in God, in so far as 
he constitutes the nature of the human mind, or the human mind
perceives those  modifications (II. xii.), and consequently (II.
xvi.) the human body itself, and as actually  existing; therefore
the mind perceives thus far only the human body.  Q.E.D.

XX. The idea or knowledge of the human mind is also in God,
following in God in the  same manner, and being referred to God
in the same manner, as the idea or knowledge of  the human body.

>>>>>Proof--Thought is an attribute of God (II. i.); therefore
(II. iii.) there must  necessarily be in God the idea both of
thought itself and of all its modifications,  consequently also
of the human mind (II. xi.).  Further, this idea or knowledge of
the mind  does not follow from God, in so far as he is infinite,
but in so far as he is affected by  another idea of an individual
thing (II. ix.).  But (II. vii.) the order and connection of
ideas  is the same as the order and connection of causes;
therefore this idea or knowledge of the  mind is in God and is
referred to God, in the same manner as the idea or knowledge of
the  body.  Q.E.D.

XXI. This idea of the mind is united to the mind in the same way
as the mind is united to  the body.

>>>>>Proof--That the mind is united to the body we have shown
from the fact, that the  body is the object of the mind (II. xii.
and xiii.); and so for the same reason the idea of the  mind must
be united with its object, that is, with the mind in the same
manner as the mind  is united to the body.  Q.E.D.

*****Note--This proposition is comprehended much more clearly
from what we have said  in the note to II. vii.  We there showed
that the idea of body and body, that is, mind and  body (II.
xiii.), are one and the same individual conceived now under the
attribute of  thought, now under the attribute of extension;
wherefore the idea of the mind and the mind  itself are one and
the same thing, which is conceived under one and the same
attribute,  namely, thought.  The idea of the mind, I repeat, and
the mind itself are in God by the  same necessity and follow from
him from the same power of thinking.  Strictly speaking,  the
idea of the mind, that is, the idea of an idea, is nothing but
the distinctive quality  (forma) of the idea in so far as it is
conceived as a mode of thought without reference to  the object;
if a man knows anything, he, by that very fact, knows that he
knows it, and at  the same time knows that he knows that he knows
it, and so on to infinity.  But I will treat  of this hereafter.

XXII. The human mind perceives not only the modifications of the
body, but also the ideas  of such modifications.

>>>>>Proof--The ideas of the ideas of modifications follow in God
in the same manner,  and are referred to God in the same manner,
as the ideas of the said modifications.  This is  proved in the
same way as II. xx.  But the ideas of the modifications of the
body are in the  human mind (II. xii.), that is, in God, in so
far as he constitutes the essence of the human  mind; therefore
the ideas of these ideas will be in God, in so far as he has the
knowledge  or idea of the human mind, that is (II. xxi.), they
will be in the human mind itself, which  therefore perceives not
only the modifications of the body, but also the ideas of such 
modifications.  Q.E.D.

XXIII. The mind does not know itself, except in so far as it
perceives the ideas of the  modifications of the body.

>>>>>Proof--The idea or knowledge of the mind (II. xx.) follows
in God in the same  manner, and is referred to God in the same
manner, as the idea or knowledge of the  body.  But since (II.
xix.) the human mind does not know the human body itself, that is
 (II. xi. Cor.), since the knowledge of the human body is not
referred to God, in so far as  he constitutes the nature of the
human mind; therefore, neither is the knowledge of the  mind
referred to God, in so far as he constitutes the essence of the
human mind; therefore  (by the same Cor. II. xi.), the human mind
thus far has no knowledge of itself.  Further the  ideas of the
modifications, whereby the body is affected, involve the nature
of the human  body itself (II. xvi.), that is (II. xiii.), they
agree with the nature of the mind; wherefore the  knowledge of
these ideas necessarily involves knowledge of the mind; but (by
the last  Prop.) the knowledge of these ideas is in the human
mind itself; wherefore the human mind  thus far only has
knowledge of itself.  Q.E.D.

XXIV. The human mind does not involve an adequate knowledge of
the parts composing  the human body.

>>>>>Proof--The parts composing the human body do not belong to
the essence of that  body, except in so far as they communicate
their motions to one another in a certain fixed  relation (Def.
after Lemma iii.), not in so far as they can be regarded as
individuals without  relation to the human body.  The parts of
the human body are highly complex individuals  (Post. i.), whose
parts (Lemma iv.) can be separated from the human body without in
any  way destroying the nature and distinctive quality of the
latter, and they can communicate  their motions (Ax. i., after
Lemma iii.) to other bodies in another relation; therefore (II.
iii.)  the idea or knowledge of each part will be in God,
inasmuch (II. ix.) as he is regarded as  affected by another idea
of a particular thing, which particular thing is prior in the
order of  nature to the aforesaid part (II. vii.).  We may affirm
the same thing of each part of each  individual composing the
human body; therefore, the knowledge of each part composing  the
human body is in God, in so far as he is affected by very many
ideas of things, and not  in so far as he has the idea of the
human body only, in other words, the idea which  constitutes the
nature of the human mind (II. xiii.); therefore (II. xi. Cor.),
the human mind  does not involve an adequate knowledge of the
human body.  Q.E.D.