Aristotle, De Anima, Book II
Part 5
Having made these distinctions let us now speak of sensation in the widest sense. Sensation depends, as we have said,
on a process of movement or affection from without, for it is held to be some sort of change of quality. Now some
thinkers assert that like is affected only by like; in what sense this is possible and in what sense impossible, we have
explained in our general discussion of acting and being acted upon.
Here arises a problem: why do we not perceive the senses themselves as well as the external objects of sense, or why
without the stimulation of external objects do they not produce sensation, seeing that they contain in themselves fire,
earth, and all the other elements, which are the direct or indirect objects is so of sense? It is clear that what is sensitive
is only potentially, not actually. The power of sense is parallel to what is combustible, for that never ignites itself
spontaneously, but requires an agent which has the power of starting ignition; otherwise it could have set itself on fire,
and would not have needed actual fire to set it ablaze.
In reply we must recall that we use the word 'perceive' in two ways, for we say (a) that what has the power to hear or
see, 'sees' or 'hears', even though it is at the moment asleep, and also (b) that what is actually seeing or hearing, 'sees' or
'hears'. Hence 'sense' too must have two meanings, sense potential, and sense actual. Similarly 'to be a sentient' means
either (a) to have a certain power or (b) to manifest a certain activity. To begin with, for a time, let us speak as if there
were no difference between (i) being moved or affected, and (ii) being active, for movement is a kind of activity-an
imperfect kind, as has elsewhere been explained. Everything that is acted upon or moved is acted upon by an agent
which is actually at work. Hence it is that in one sense, as has already been stated, what acts and what is acted upon are
like, in another unlike, i.e. prior to and during the change the two factors are unlike, after it like.
But we must now distinguish not only between what is potential and what is actual but also different senses in which
things can be said to be potential or actual; up to now we have been speaking as if each of these phrases had only one
sense. We can speak of something as 'a knower' either (a) as when we say that man is a knower, meaning that man falls
within the class of beings that know or have knowledge, or (b) as when we are speaking of a man who possesses a
knowledge of grammar; each of these is so called as having in him a certain potentiality, but there is a difference
between their respective potentialities, the one (a) being a potential knower, because his kind or matter is such and
such, the other (b), because he can in the absence of any external counteracting cause realize his knowledge in actual
knowing at will. This implies a third meaning of 'a knower' (c), one who is already realizing his knowledge-he is a
knower in actuality and in the most proper sense is knowing, e.g. this A. Both the former are potential knowers, who
realize their respective potentialities, the one (a) by change of quality, i.e. repeated transitions from one state to its
opposite under instruction, the other (b) by the transition from the inactive possession of sense or grammar to their
active exercise. The two kinds of transition are distinct.
Also the expression 'to be acted upon' has more than one meaning; it may mean either (a) the extinction of one of two
contraries by the other, or (b) the maintenance of what is potential by the agency of what is actual and already like what
is acted upon, with such likeness as is compatible with one's being actual and the other potential. For what possesses
knowledge becomes an actual knower by a transition which is either not an alteration of it at all (being in reality a
development into its true self or actuality) or at least an alteration in a quite different sense from the usual meaning.
Hence it is wrong to speak of a wise man as being 'altered' when he uses his wisdom, just as it would be absurd to
speak of a builder as being altered when he is using his skill in building a house.
What in the case of knowing or understanding leads from potentiality to actuality ought not to be called teaching but
something else. That which starting with the power to know learns or acquires knowledge through the agency of one
who actually knows and has the power of teaching either (a) ought not to be said 'to be acted upon' at all or (b) we must
recognize two senses of alteration, viz. (i) the substitution of one quality for another, the first being the contrary of the
second, or (ii) the development of an existent quality from potentiality in the direction of fixity or nature.
In the case of what is to possess sense, the first transition is due to the action of the male parent and takes place before
birth so that at birth the living thing is, in respect of sensation, at the stage which corresponds to the possession of
knowledge. Actual sensation corresponds to the stage of the exercise of knowledge. But between the two cases
compared there is a difference; the objects that excite the sensory powers to activity, the seen, the heard, &c., are
outside. The ground of this difference is that what actual sensation apprehends is individuals, while what knowledge
apprehends is universals, and these are in a sense within the soul. That is why a man can exercise his knowledge when
he wishes, but his sensation does not depend upon himself a sensible object must be there. A similar statement must be
made about our knowledge of what is sensible-on the same ground, viz. that the sensible objects are individual and
external.
A later more appropriate occasion may be found thoroughly to clear up all this. At present it must be enough to
recognize the distinctions already drawn; a thing may be said to be potential in either of two senses, (a) in the sense in
which we might say of a boy that he may become a general or (b) in the sense in which we might say the same of an
adult, and there are two corresponding senses of the term 'a potential sentient'. There are no separate names for the two
stages of potentiality; we have pointed out that they are different and how they are different. We cannot help using the
incorrect terms 'being acted upon or altered' of the two transitions involved. As we have said, has the power of
sensation is potentially like what the perceived object is actually; that is, while at the beginning of the process of its
being acted upon the two interacting factors are dissimilar, at the end the one acted upon is assimilated to the other and
is identical in quality with it.
Part 6
In dealing with each of the senses we shall have first to speak of the objects which are perceptible by each. The term
'object of sense' covers three kinds of objects, two kinds of which are, in our language, directly perceptible, while the
remaining one is only incidentally perceptible. Of the first two kinds one (a) consists of what is perceptible by a single
sense, the other (b) of what is perceptible by any and all of the senses. I call by the name of special object of this or that
sense that which cannot be perceived by any other sense than that one and in respect of which no error is possible; in
this sense colour is the special object of sight, sound of hearing, flavour of taste. Touch, indeed, discriminates more
than one set of different qualities. Each sense has one kind of object which it discerns, and never errs in reporting that
what is before it is colour or sound (though it may err as to what it is that is coloured or where that is, or what it is that
is sounding or where that is.) Such objects are what we propose to call the special objects of this or that sense.
'Common sensibles' are movement, rest, number, figure, magnitude; these are not peculiar to any one sense, but are
common to all. There are at any rate certain kinds of movement which are perceptible both by touch and by sight.
We speak of an incidental object of sense where e.g. the white object which we see is the son of Diares; here because
'being the son of Diares' is incidental to the directly visible white patch we speak of the son of Diares as being
(incidentally) perceived or seen by us. Because this is only incidentally an object of sense, it in no way as such affects
the senses. Of the two former kinds, both of which are in their own nature perceptible by sense, the first kind-that of
special objects of the several senses-constitute the objects of sense in the strictest sense of the term and it is to them
that in the nature of things the structure of each several sense is adapted.
Part 7
The object of sight is the visible, and what is visible is (a) colour and (b) a certain kind of object which can be
described in words but which has no single name; what we mean by (b) will be abundantly clear as we proceed.
Whatever is visible is colour and colour is what lies upon what is in its own nature visible; 'in its own nature' here
means not that visibility is involved in the definition of what thus underlies colour, but that that substratum contains in
itself the cause of visibility. Every colour has in it the power to set in movement what is actually transparent; that
power constitutes its very nature. That is why it is not visible except with the help of light; it is only in light that the
colour of a thing is seen. Hence our first task is to explain what light is.
Now there clearly is something which is transparent, and by 'transparent' I mean what is visible, and yet not visible in
itself, but rather owing its visibility to the colour of something else; of this character are air, water, and many solid
bodies. Neither air nor water is transparent because it is air or water; they are transparent because each of them has
contained in it a certain substance which is the same in both and is also found in the eternal body which constitutes the
uppermost shell of the physical Cosmos. Of this substance light is the activity-the activity of what is transparent so far
forth as it has in it the determinate power of becoming transparent; where this power is present, there is also the
potentiality of the contrary, viz. darkness. Light is as it were the proper colour of what is transparent, and exists
whenever the potentially transparent is excited to actuality by the influence of fire or something resembling 'the
uppermost body'; for fire too contains something which is one and the same with the substance in question.
We have now explained what the transparent is and what light is; light is neither fire nor any kind whatsoever of body
nor an efflux from any kind of body (if it were, it would again itself be a kind of body)-it is the presence of fire or
something resembling fire in what is transparent. It is certainly not a body, for two bodies cannot be present in the same
place. The opposite of light is darkness; darkness is the absence from what is transparent of the corresponding positive
state above characterized; clearly therefore, light is just the presence of that.
Empedocles (and with him all others who used the same forms of expression) was wrong in speaking of light as
'travelling' or being at a given moment between the earth and its envelope, its movement being unobservable by us; that
view is contrary both to the clear evidence of argument and to the observed facts; if the distance traversed were short,
the movement might have been unobservable, but where the distance is from extreme East to extreme West, the draught
upon our powers of belief is too great.
What is capable of taking on colour is what in itself is colourless, as what can take on sound is what is soundless; what
is colourless includes (a) what is transparent and (b) what is invisible or scarcely visible, i.e. what is 'dark'. The latter
(b) is the same as what is transparent, when it is potentially, not of course when it is actually transparent; it is the same
substance which is now darkness, now light.
Not everything that is visible depends upon light for its visibility. This is only true of the 'proper' colour of things.
Some objects of sight which in light are invisible, in darkness stimulate the sense; that is, things that appear fiery or
shining. This class of objects has no simple common name, but instances of it are fungi, flesh, heads, scales, and eyes
of fish. In none of these is what is seen their own proper' colour. Why we see these at all is another question. At present
what is obvious is that what is seen in light is always colour. That is why without the help of light colour remains
invisible. Its being colour at all means precisely its having in it the power to set in movement what is already actually
transparent, and, as we have seen, the actuality of what is transparent is just light.
The following experiment makes the necessity of a medium clear. If what has colour is placed in immediate contact
with the eye, it cannot be seen. Colour sets in movement not the sense organ but what is transparent, e.g. the air, and
that, extending continuously from the object to the organ, sets the latter in movement. Democritus misrepresents the
facts when he expresses the opinion that if the interspace were empty one could distinctly see an ant on the vault of the
sky; that is an impossibility. Seeing is due to an affection or change of what has the perceptive faculty, and it cannot be
affected by the seen colour itself; it remains that it must be affected by what comes between. Hence it is indispensable
that there be something in between-if there were nothing, so far from seeing with greater distinctness, we should see
nothing at all.
We have now explained the cause why colour cannot be seen otherwise than in light. Fire on the other hand is seen
both in darkness and in light; this double possibility follows necessarily from our theory, for it is just fire that makes
what is potentially transparent actually transparent.
The same account holds also of sound and smell; if the object of either of these senses is in immediate contact with the
organ no sensation is produced. In both cases the object sets in movement only what lies between, and this in turn sets
the organ in movement: if what sounds or smells is brought into immediate contact with the organ, no sensation will be
produced. The same, in spite of all appearances, applies also to touch and taste; why there is this apparent difference
will be clear later. What comes between in the case of sounds is air; the corresponding medium in the case of smell has
no name. But, corresponding to what is transparent in the case of colour, there is a quality found both in air and water,
which serves as a medium for what has smell-I say 'in water' because animals that live in water as well as those that
live on land seem to possess the sense of smell, and 'in air' because man and all other land animals that breathe,
perceive smells only when they breathe air in. The explanation of this too will be given later.
John Locke Essay Concerning Human Understanding, Book II
Chapter II
Of Simple Ideas
1.Uncompounded appearances. The better to understand the nature, manner, and extent of our knowledge, one thing is
carefully to be observed concerning the ideas we have; and that is, that some of them are simple and some complex.
Though the qualities that affect our senses are, in the things themselves, so united and blended, that there is no
separation, no distance between them; yet it is plain, the ideas they produce in the mind enter by the senses simple and
unmixed. For, though the sight and touch often take in from the same object, at the same time, different ideas;- as a
man sees at once motion and colour; the hand feels softness and warmth in the same piece of wax: yet the simple ideas
thus united in the same subject, are as perfectly distinct as those that come in by different senses. The coldness and
hardness which a man feels in a piece of ice being as distinct ideas in the mind as the smell and whiteness of a lily; or
as the taste of sugar, and smell of a rose. And there is nothing can be plainer to a man than the clear and distinct
perception he has of those simple ideas; which, being each in itself uncompounded, contains in it nothing but one
uniform appearance, or conception in the mind, and is not distinguishable into different ideas.
2. The mind can neither make nor destroy them. These simple ideas, the materials of all our knowledge, are suggested
and furnished to the mind only by those two ways above mentioned, viz. sensation and reflection. When the
understanding is once stored with these simple ideas, it has the power to repeat, compare, and unite them, even to an
almost infinite variety, and so can make at pleasure new complex ideas. But it is not in the power of the most exalted
wit, or enlarged understanding, by any quickness or variety of thought, to invent or frame one new simple idea in the
mind, not taken in by the ways before mentioned: nor can any force of the understanding destroy those that are there.
The dominion of man, in this little world of his own understanding being muchwhat the same as it is in the great world
of visible things; wherein his power, however managed by art and skill, reaches no farther than to compound and divide
the materials that are made to his hand; but can do nothing towards the making the least particle of new matter, or
destroying one atom of what is already in being. The same inability will every one find in himself, who shall go about
to fashion in his understanding one simple idea, not received in by his senses from external objects, or by reflection
from the operations of his own mind about them. I would have any one try to fancy any taste which had never affected
his palate; or frame the idea of a scent he had never smelt: and when he can do this, I will also conclude that a blind
man hath ideas of colours, and a deaf man true distinct notions of sounds.
3. Only the qualities that affect the senses are imaginable. This is the reason why- though we cannot believe it
impossible to God to make a creature with other organs, and more ways to convey into the understanding the notice of
corporeal things than those five, as they are usually counted, which he has given to man- yet I think it is not possible
for any man to imagine any other qualities in bodies, howsoever constituted, whereby they can be taken notice of,
besides sounds, tastes, smells, visible and tangible qualities. And had mankind been made but with four senses, the
qualities then which are the objects of the fifth sense had been as far from our notice, imagination, and conception, as
now any belonging to a sixth, seventh, or eighth sense can possibly be;- which, whether yet some other creatures, in
some other parts of this vast and stupendous universe, may not have, will be a great presumption to deny. He that will
not set himself proudly at the top of all things, but will consider the immensity of this fabric, and the great variety that
is to be found in this little and inconsiderable part of it which he has to do with, may be apt to think that, in other
mansions of it, there may be other and different intelligent beings, of whose faculties he has as little knowledge or
apprehension as a worm shut up in one drawer of a cabinet hath of the senses or understanding of a man; such variety
and excellency being suitable to the wisdom and power of the Maker. I have here followed the common opinion of
man's having but five senses; though, perhaps, there may be justly counted more;- but either supposition serves equally
to my present purpose.
Chapter III
Of Simple Ideas of Sense
1. Division of simple ideas. The better to conceive the ideas we receive from sensation, it may not be amiss for us to
consider them, in reference to the different ways whereby they make their approaches to our minds, and make
themselves perceivable by us.
First, then, There are some which come into our minds by one sense only.
Secondly, There are others that convey themselves into the mind by more senses than one.
Thirdly, Others that are had from reflection only.
Fourthly, There are some that make themselves way, and are suggested to the mind by all the ways of sensation and
reflection.
We shall consider them apart under these several heads.
Ideas of one sense. There are some ideas which have admittance only through one sense, which is peculiarly adapted to
receive them. Thus light and colours, as white, red, yellow, blue; with their several degrees or shades and mixtures, as
green, scarlet, purple, sea-green, and the rest, come in only by the eyes. All kinds of noises, sounds, and tones, only by
the ears. The several tastes and smells, by the nose and palate. And if these organs, or the nerves which are the conduits
to convey them from without to their audience in the brain,- the mind's presence-room (as I may so call it)- are any of
them so disordered as not to perform their functions, they have no postern to be admitted by; no other way to bring
themselves into view, and be perceived by the understanding.
The most considerable of those belonging to the touch, are heat and cold, and solidity: all the rest, consisting almost
wholly in the sensible configuration, as smooth and rough; or else, more or less firm adhesion of the parts, as hard and
soft, tough and brittle, are obvious enough.
2.Few simple ideas have names. I think it will be needless to enumerate all the particular simple ideas belonging to
each sense. Nor indeed is it possible if we would; there being a great many more of them belonging to most of the
senses than we have names for. The variety of smells, which are as many almost, if not more, than species of bodies in
the world, do most of them want names. Sweet and stinking commonly serve our turn for these ideas, which in effect is
little more than to call them pleasing or displeasing; though the smell of a rose and violet, both sweet, are certainly very
distinct ideas. Nor are the different tastes, that by our palates we receive ideas of, much better provided with names.
Sweet, bitter, sour, harsh, and salt are almost all the epithets we have to denominate that numberless variety of relishes,
which are to be found distinct, not only in almost every sort of creatures, but in the different parts of the same plant,
fruit, or animal. The same may be said of colours and sounds. I shall, therefore, in the account of simple ideas I am here
giving, content myself to set down only such as are most material to our present purpose, or are in themselves less apt
to be taken notice of though they are very frequently the ingredients of our complex ideas; amongst which, I think, I
may well account solidity, which therefore I shall treat of in the next chapter.
8.Our ideas and the qualities of bodies. Whatsoever the mind perceives in itself, or is the immediate object of
perception, thought, or understanding, that I call idea; and the power to produce any idea in our mind, I call quality of
the subject wherein that power is. Thus a snowball having the power to produce in us the ideas of white, cold, and
round,- the power to produce those ideas in us, as they are in the snowball, I call qualities; and as they are sensations or
perceptions in our understandings, I call them ideas; which ideas, if I speak of sometimes as in the things themselves, I
would be understood to mean those qualities in the objects which produce them in us.
9. Primary qualities of bodies. Qualities thus considered in bodies are,
First, such as are utterly inseparable from the body, in what state soever it be; and such as in all the alterations and
changes it suffers, all the force can be used upon it, it constantly keeps; and such as sense constantly finds in every
particle of matter which has bulk enough to be perceived; and the mind finds inseparable from every particle of matter,
though less than to make itself singly be perceived by our senses: v.g. Take a grain of wheat, divide it into two parts;
each part has still solidity, extension, figure, and mobility: divide it again, and it retains still the same qualities; and so
divide it on, till the parts become insensible; they must retain still each of them all those qualities. For division (which
is all that a mill, or pestle, or any other body, does upon another, in reducing it to insensible parts) can never take away
either solidity, extension, figure, or mobility from any body, but only makes two or more distinct separate masses of
matter, of that which was but one before; all which distinct masses, reckoned as so many distinct bodies, after division,
make a certain number. These I call original or primary qualities of body, which I think we may observe to produce
simple ideas in us, viz. solidity, extension, figure, motion or rest, and number.
10. Secondary qualities of bodies. Secondly, such qualities which in truth are nothing in the objects themselves but
power to produce various sensations in us by their primary qualities, i.e. by the bulk, figure, texture, and motion of their
insensible parts, as colours, sounds, tastes, &c. These I call secondary qualities. To these might be added a third sort,
which are allowed to be barely powers; though they are as much real qualities in the subject as those which I, to comply
with the common way of speaking, call qualities, but for distinction, secondary qualities. For the power in fire to
produce a new colour, or consistency, in wax or clay,- by its primary qualities, is as much a quality in fire, as the
power it has to produce in me a new idea or sensation of warmth or burning, which I felt not before,- by the same
primary qualities, viz. the bulk, texture, and motion of its insensible parts.
13. How secondary qualities produce their ideas. After the same manner, that the ideas of these original qualities are
produced in us, we may conceive that the ideas of secondary qualities are also produced, viz. by the operation of
insensible particles on our senses. For, it being manifest that there are bodies and good store of bodies, each whereof
are so small, that we cannot by any of our senses discover either their bulk, figure, or motion,- as is evident in the
particles of the air and water, and others extremely smaller than those; perhaps as much smaller than the particles of air
and water, as the particles of air and water are smaller than peas or hail-stones;- let us suppose at present that the
different motions and figures, bulk and number, of such particles, affecting the several organs of our senses, produce in
us those different sensations which we have from the colours and smells of bodies; v.g. that a violet, by the impulse of
such insensible particles of matter, of peculiar figures and bulks, and in different degrees and modifications of their
motions, causes the ideas of the blue colour, and sweet scent of that flower to be produced in our minds. It being no
more impossible to conceive that God should annex such ideas to such motions, with which they have no similitude,
than that he should annex the idea of pain to the motion of a piece of steel dividing our flesh, with which that idea hath
no resemblance.
Hume: Treatise of Human Nature, Book 1, Part I
Of the Origin of our Ideas.
All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call IMPRESSIONS
and IDEAS. The difference betwixt these consists in the degrees of force and liveliness, with which they strike upon
the mind, and make their way into our thought or consciousness. Those perceptions, which enter with most force and
violence, we may name impressions: and under this name I comprehend all our sensations, passions and emotions, as
they make their first appearance in the soul. By ideas I mean the faint images of these in thinking and reasoning; such
as, for instance, are all the perceptions excited by the present discourse, excepting only those which arise from the sight
and touch, and excepting the immediate pleasure or uneasiness it may occasion. I believe it will not be very necessary
to employ many words in explaining this distinction. Every one of himself will readily perceive the difference betwixt
feeling and thinking. The common degrees of these are easily distinguished; tho' it is not impossible but in particular
instances they may very nearly approach to each other. Thus in sleep, in a fever, in madness, or in any very violent
emotions of soul, our ideas may approach to our impressions, As on the other hand it sometimes happens, that our
impressions are so faint and low, that we cannot distinguish them from our ideas. But notwithstanding this near
resemblance in a few instances, they are in general so very different, that no-one can make a scruple to rank them
under distinct heads, and assign to each a peculiar name to mark the difference.(1)
There is another division of our perceptions, which it will be convenient to observe, and which extends itself both to
our impressions and ideas. This division is into SIMPLE and COMPLEX. Simple perceptions or impressions and ideas
are such as admit of no distinction nor separation. The complex are the contrary to these, and may be distinguished into
parts. Tho' a particular colour, taste, and smell, are qualities all united together in this apple, 'tis easy to perceive they
are not the same, but are at least distinguishable from each other.
Having by these divisions given an order and arrangement to our objects, we may now apply ourselves to consider with
the more accuracy their qualities and relations. The first circumstance, that strikes my eye, is the great resemblance
betwixt our impressions and ideas in every other particular, except their degree of force and vivacity. The one seem to
be in a manner the reflexion of the other; so that all the perceptions of the mind are double., and appear both as
impressions and ideas. When I shut my eyes and think of my chamber, the ideas I form are exact representations of the
impressions I felt; nor is there any circumstance of the one, which is not to be found in the other. In running over my
other perceptions, I find still the same resemblance and representation. Ideas and impressions appear always to
correspond to each other. This circumstance seems to me remarkable, and engages my attention for a moment.
Upon a more accurate survey I find I have been carried away too far by the first appearance, and that I must make use
of the distinction of perceptions into simple and complex, to limit this general decision, that all our ideas and
impressions are resembling. I observe, that many of our complex ideas never had impressions, that corresponded to
them, and that many of our complex impressions never are exactly copied in ideas. I can imagine to myself such a city
as the New Jerusalem, whose pavement is gold and walls are rubies, tho' I never saw any such. I have seen Paris; but
shall I affirm I can form such an idea of that city, as will perfectly represent all its streets and houses in their real and
just proportions?
I perceive, therefore, that tho' there is in general a great, resemblance betwixt our complex impressions and ideas, yet
the rule is not universally true, that they are exact copies of each other. We may next consider how the case stands with
our simple, perceptions. After the most accurate examination, of which I am capable, I venture to affirm, that the rule
here holds without any exception, and that every simple idea has a simple impression, which resembles it, and every
simple impression a correspondent idea. That idea of red, which we form in the dark, and that impression which strikes
our eyes in sun-shine, differ only in degree, not in nature. That the case is the same with all our simple impressions and
ideas, 'tis impossible to prove by a particular enumeration of them. Every one may satisfy himself in this point by
running over as many as he pleases. But if any one should deny this universal resemblance, I know no way of
convincing him, but by desiring him to shew a simple impression, that has not a correspondent idea, or a simple idea,
that has not a correspondent impression. If he does not answer this challenge, as 'tis certain he can-not, we may from
his silence and our own observation establish our conclusion.
Thus we find, that all simple ideas and impressions resemble each other; and as the complex are formed from them, we
may affirm in general, that these two species of perception are exactly correspondent. Having discovered this relation,
which requires no farther examination, I am curious to find some other of their qualities. Let us consider how. they
stand with regard to their existence, and which of the impressions and ideas are causes, and which effects.
The full examination of this question is the subject of the present treatise; and therefore we shall here content ourselves
with establishing one general proposition, That all our simple ideas in their first appearance are deriv'd from simple
impressions, which are correspondent to them, and which they exactly represent.
In seeking for phenomena to prove this proposition, I find only those of two kinds; but in each kind the phenomena are
obvious, numerous, and conclusive. I first make myself certain, by a new, review, of what I have already asserted, that
every simple impression is attended with a correspondent idea, and every simple idea with a correspondent impression.
From this constant conjunction of resembling perceptions I immediately conclude, that there is a great connexion
betwixt our correspondent impressions and ideas, and that the existence of the one has a -considerable influence upon
that of the other. Such a constant conjunction, in such an infinite number of instances, can never arise from chance; but
clearly proves a dependence of the impressions on the ideas, or of the ideas on the impressions. That I may know on
which side this dependence lies, I consider the order of their first appearance; and find by constant experience, that the
simple impressions always take the precedence of their correspondent ideas, but never appear in the contrary order. To
give a child an idea of scarlet or orange, of sweet or bitter, I present the objects, or in other words, convey to him these
impressions; but proceed not so absurdly, as to endeavour to produce -the impressions by exciting the ideas. Our ideas
upon their appearance produce not their correspondent impressions, nor do we perceive any colour, or feel any
sensation merely upon thinking of them. On the other hand we find, that any impression either of the mind or body is
constantly followed by an idea, which resembles it, and is only different in the degrees of force and liveliness, The
constant conjunction of our resembling perceptions, is a convincing proof, that the one are the causes of the other; and
this priority of the impressions is an equal proof, that our impressions are the causes of our ideas, not our ideas .of our,
impressions.
To confirm this I consider Another plain and convincing phaenomenon; which is, that, where-ever by any accident the
faculties, which give rise to any impressions, are obstructed in their operations, as when one is born blind or deaf; -not
only the impressions are lost, but also their correspondent ideas; so that there never appear in the mind the least traces
of either of them. Nor is this only true, where the organs of sensation are entirely destroy'd, but likewise where they
have never been put in action to produce a particular impression. We cannot form to ourselves a just idea of the taste of
a pine apple, without having actually tasted it.
There is however one contradictory phaenomenon, which may prove, that 'tis not absolutely impossible for ideas to go
before their correspondent impressions. I believe it will readily be allow'd that the several distinct ideas of colours,
which enter by the eyes, or those of sounds, which are convey'd by the hearing, are really different from each other, tho'
at the same time resembling. Now if this be true of different colours, it must be no less so of the different shades of the
same colour, that each of them produces a distinct idea, independent of the rest. For if this shou'd be deny'd, 'tis
possible, by the continual gradation of shades, to run a colour insensibly into what is most remote from it; and if you
will not allow any of the means to be different, you cannot without absurdity deny the extremes to be the same.
Suppose therefore a person to have enjoyed his sight for thirty years, and to have become perfectly well acquainted
with colours of all kinds, excepting one particular shade of blue, for instance, which it never has been his fortune to
meet with. Let all the different shades of that colour, except that single one, be plac'd before him, descending gradually
from the deepest to the lightest; 'tis plain, that he will perceive a blank, where that shade is wanting, said will be
sensible, that there is a greater distance in that place betwixt the contiguous colours, than in any other. Now I ask,
whether 'tis possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of
that particular shade, tho' it had never been conveyed to him by his senses? I believe i here are few but will be of
opinion that he can; and this may serve as a proof, that the simple ideas are not always derived from the correspondent
impressions; tho' the instance is so particular and singular, that 'tis scarce worth our observing, and does not merit that
for it alone we should alter our general maxim.
But besides this exception, it may not be amiss to remark on this head, that the principle of the priority of impressions
to ideas must be understood with another limitation, viz., that as our ideas are images of our impressions, so we can
form secondary ideas, which are images of the primary; as appears from this very reasoning concerning them. This is
not, properly speaking, an exception to the rule so much as an explanation of it. Ideas produce the images of them.
selves in new ideas; but as the first ideas are supposed to be derived from impressions, it still remains true, that all our
simple ideas proceed either mediately or immediately, from their correspondent impressions.
This then is the first principle I establish in the science of human nature; nor ought we to despise it because of the
simplicity of its appearance. For 'tis remarkable, that the present question concerning the precedency of our impressions
or ideas, is the same with what has made so much noise in other terms, when it has been disputed whether there be any
innate ideas, or whether all ideas be derived from sensation and reflexion. We may observe, that in order to prove the
ideas of extension and colour not to be innate, philosophers do nothing but shew that they are conveyed by our senses.
To prove the ideas of passion and desire not to be innate, they observe that we have a preceding experience of these
emotions in ourselves., Now if we carefully examine these arguments, we shall find that they prove nothing but that
ideas are preceded by other more lively perceptions, from which the are derived, and which they represent. I hope this
clear stating of the question will remove all disputes concerning it, and win render this principle of more use in our
reasonings, than it seems hitherto to have been.
Berkeley Principles
9. Some there are who make a distinction betwixt primary and secondary qualities. By the former they mean extension,
figure, motion, rest, solidity or impenetrability, and number; by the latter they denote all other sensible qualities, as
colours, sounds, tastes, and so forth. The ideas we have of these they acknowledge not to be the resemblances of
anything existing without the mind, or unperceived, but they will have our ideas of the primary qualities to be patterns
or images of things which exist without the mind, in an unthinking substance which they call Matter. By Matter,
therefore, we are to understand an inert, senseless substance, in which extension, figure, and motion do actually subsist.
But it is evident from what we have already shown, that extension, figure, and motion are only ideas existing in the
mind, and that an idea can be like nothing but another idea, and that consequently neither they nor their archetypes can
exist in an unperceiving substance. Hence, it is plain that that the very notion of what is called Matter or corporeal
substance, involves a contradiction in it.
10. They who assert that figure, motion, and the rest of the primary or original qualities do exist without the mind in
unthinking substances, do at the same time acknowledge that colours, sounds, heat cold, and suchlike secondary
qualities, do not- which they tell us are sensations existing in the mind alone, that depend on and are occasioned by the
different size, texture, and motion of the minute particles of matter. This they take for an undoubted truth, which they
can demonstrate beyond all exception. Now, if it be certain that those original qualities are inseparably united with the
other sensible qualities, and not, even in thought, capable of being abstracted from them, it plainly follows that they
exist only in the mind. But I desire any one to reflect and try whether he can, by any abstraction of thought, conceive
the extension and motion of a body without all other sensible qualities. For my own part, I see evidently that it is not in
my power to frame an idea of a body extended and moving, but I must withal give it some colour or other sensible
quality which is acknowledged to exist only in the mind. In short, extension, figure, and motion, abstracted from all
other qualities, are inconceivable. Where therefore the other sensible qualities are, there must these be also, to wit, in
the mind and nowhere else.
Berkeley: Theory of Vision
43. And perhaps upon a strict inquiry we shall not find that even those who from their birth have grown up in a
continued habit of seeing are irrecoverably prejudiced on the other side, to wit, in thinking what they see to be at a
distance from them. For at this time it seems agreed on all hands, by those who have had any thoughts of that matter,
that colours, which are the proper and immediate object of sight, are not without the mind. But then it will be said, by
sight we have also the ideas of extension, and figure, and motion; all which may well be thought without, and at some
distance from the mind, though colour should not. In answer to this I appeal to any man's experience, whether the
visible extension of any object doth not appear as near to him as the colour of that object; nay, whether they do not both
seem to be in the very same place. Is not the extension we see coloured, and is it possible for us, so much as in thought,
to separate and abstract colour from extension? Now, where the extension is there surely is the figure, and there the
motion too. I speak of those which are perceived by sight.