An Essay Concerning Humane Understanding, Volume II. - John Locke
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But to return to the argument in hand: our knowledge, I say, is not only
limited to the paucity and imperfections of the ideas we have, and which
we employ it about, but even comes short of that too: but how far it
reaches, let us now inquire.
7. How far our Knowledge reaches.
The affirmations or negations we make concerning the ideas we have, may,
as I have before intimated in general, be reduced to these four sorts,
viz. identity, co-existence, relation, and real existence. I shall
examine how far our knowledge extends in each of these:
8. Firstly, Our Knowledge of Identity and Diversity in ideas extends as
far as our Ideas themselves.
FIRST, as to IDENTITY and DIVERSITY. In this way of agreement or
disagreement of our ideas, our intuitive knowledge is as far extended
as our ideas themselves: and there can be no idea in the mind, which it
does not, presently, by an intuitive knowledge, perceive to be what it
is, and to be different from any other.
9. Secondly, Of their Co-existence, extends only a very little way.
SECONDLY, as to the second sort, which is the agreement or disagreement
of our ideas in CO-EXISTENCE, in this our knowledge is very short;
though in this consists the greatest and most material part of our
knowledge concerning substances. For our ideas of the species of
substances being, as I have showed, nothing but certain collections of
simple ideas united in one subject, and so co-existing together; v.g.
our idea of flame is a body hot, luminous, and moving upward; of gold,
a body heavy to a certain degree, yellow, malleable, and fusible: for
these, or some such complex ideas as these, in men's minds, do these two
names of the different substances, flame and gold, stand for. When we
would know anything further concerning these, or any other sort of
substances, what do we inquire, but what OTHER qualities or powers these
substances have or have not? Which is nothing else but to know what
OTHER simple ideas do, or do not co-exist with those that make up that
complex idea?
10. Because the Connexion between simple Ideas in substances is for the
most part unknown.
This, how weighty and considerable a part soever of human science, is
yet very narrow, and scarce any at all. The reason whereof is, that the
simple ideas whereof our complex ideas of substances are made up are,
for the most part, such as carry with them, in their own nature, no
VISIBLE NECESSARY connexion or inconsistency with any other simple
ideas, whose co-existence with them we would inform ourselves about.
11. Especially of the secondary Qualities of Bodies.
The ideas that our complex ones of substances are made up of, and about
which our knowledge concerning substances is most employed, are those of
their secondary qualities; which depending all (as has been shown) upon
the primary qualities of their minute and insensible parts; or, if not
upon them, upon something yet more remote from our comprehension; it is
impossible we should know which have a NECESSARY union or inconsistency
one with another. For, not knowing the root they spring from, not
knowing what size, figure, and texture of parts they are, on which
depend, and from which result those qualities which make our complex
idea of gold, it is impossible we should know what OTHER qualities
result from, or are incompatible with, the same constitution of the
insensible parts of gold; and so consequently must always co-exist with
that complex idea we have of it, or else are inconsistent with it.
12. Because necessary Connexion between any secondary and the primary
Qualities is undiscoverable by us.
Besides this ignorance of the primary qualities of the insensible parts
of bodies, on which depend all their secondary qualities, there is yet
another and more incurable part of ignorance, which sets us more remote
from a certain knowledge of the co-existence or INCO-EXISTENCE (if I may
so say) of different ideas in the same subject; and that is, that there
is no discoverable connexion between any secondary quality and those
primary qualities which it depends on.
13. We have no perfect knowledge of their Primary Qualities.
That the size, figure, and motion of one body should cause a change
in the size, figure, and motion of another body, is not beyond our
conception; the separation of the parts of one body upon the intrusion
of another; and the change from rest to motion upon impulse; these and
the like seem to have SOME CONNEXION one with another. And if we knew
these primary qualities of bodies, we might have reason to hope we might
be able to know a great deal more of these operations of them one upon
another: but our minds not being able to discover any connexion betwixt
these primary qualities of bodies and the sensations that are produced
in us by them, we can never be able to establish certain and undoubted
rules of the CONSEQUENCE or CO-EXISTENCE of any secondary qualities,
though we could discover the size, figure, or motion of those invisible
parts which immediately produce them. We are so far from knowing WHAT
figure, size, or motion of parts produce a yellow colour, a sweet taste,
or a sharp sound, that we can by no means conceive how ANY size, figure,
or motion of any particles, can possibly produce in us the idea of any
colour, taste, or sound whatsoever: there is no conceivable connexion
between the one and the other.
14. And seek in vain for certain and universal knowledge of unperceived
qualities in substances.
In vain, therefore, shall we endeavour to discover by our ideas (the
only true way of certain and universal knowledge) what other ideas are
to be found constantly joined with that of OUR complex idea of any
substance: since we neither know the real constitution of the minute
parts on which their qualities do depend; nor, did we know them,
could we discover any necessary connexion between them and any of
the secondary qualities: which is necessary to be done before we can
certainly know their necessary co-existence. So, that, let our complex
idea of any species of substances be what it will, we can hardly, from
the simple ideas contained in it, certainly determine the necessary
co-existence of any other quality whatsoever. Our knowledge in all these
inquiries reaches very little further than our experience. Indeed some
few of the primary qualities have a necessary dependence and visible
connexion one with another, as figure necessarily supposes extension;
receiving or communicating motion by impulse, supposes solidity. But
though these, and perhaps some others of our ideas have: yet there are
so few of them that have a visible connexion one with another, that we
can by intuition or demonstration discover the co-existence of very few
of the qualities that are to be found united in substances: and we are
left only to the assistance of our senses to make known to us what
qualities they contain. For of all the qualities that are co-existent
in any subject, without this dependence and evident connexion of their
ideas one with another, we cannot know certainly any two to co-exist,
any further than experience, by our senses, informs us. Thus, though we
see the yellow colour, and, upon trial, find the weight, malleableness,
fusibility, and fixedness that are united in a piece of gold; yet,
because no one of these ideas has any evident dependence or necessary
connexion with the other, we cannot certainly know that where any four
of these are, the fifth will be there also, how highly probable soever
it may be; because the highest probability amounts not to certainty,
without which there can be no true knowledge. For this co-existence can
be no further known than it is perceived; and it cannot be perceived but
either in particular subjects, by the observation of our senses, or, in
general, by the necessary connexion of the ideas themselves.
15. Of Repugnancy to co-exist, our knowledge is larger.
As to the incompatibility or repugnancy to co-existence, we may know
that any subject may have of each sort of primary qualities but one
particular at once: v.g. each particular extension, figure, number of
parts, motion, excludes all other of each kind. The like also is certain
of all sensible ideas peculiar to each sense; for whatever of each kind
is present in any subject, excludes all other of that sort: v.g. no one
subject can have two smells or two colours at the same time. To this,
perhaps will be said, Has not an opal, or the infusion of LIGNUM
NEPHRITICUM, two colours at the same time? To which I answer, that
these bodies, to eyes differently, placed, may at the same time afford
different colours: but I take liberty also to say, that, to eyes
differently placed, it is different parts of the object that reflect the
particles of light: and therefore it is not the same part of the object,
and so not the very same subject, which at the same time appears both
yellow and azure. For, it is as impossible that the very same particle
of any body should at the same time differently modify or reflect the
rays of light, as that it should have two different figures and textures
at the same time.
16. Our Knowledge of the Co-existence of Power in Bodies extends but a
very little Way.
But as to the powers of substances to change the sensible qualities of
other bodies, which make a great part of our inquiries about them, and
is no inconsiderable branch of our knowledge; I doubt as to these,
whether our knowledge reaches much further than our experience; or
whether we can come to the discovery of most of these powers, and be
certain that they are in any subject, by the connexion with any of those
ideas which to us make its essence. Because the active and passive
powers of bodies, and their ways of operating, consisting in a texture
and motion of parts which we cannot by any means come to discover; it is
but in very few cases we can be able to perceive their dependence on,
or repugnance to, any of those ideas which make our complex one of that
sort of things. I have here instanced in the corpuscularian hypothesis,
as that which is thought to go furthest in an intelligible explication
of those qualities of bodies; and I fear the weakness of human
understanding is scarce able to substitute another, which will afford
us a fuller and clearer discovery of the necessary connexion and
co-existence of the powers which are to be observed united in several
sorts of them. This at least is certain, that, whichever hypothesis be
clearest and truest, (for of that it is not my business to determine,)
our knowledge concerning corporeal substances will be very little
advanced by any of them, till we are made to see what qualities and
powers of bodies have a NECESSARY connexion or repugnancy one with
another; which in the present state of philosophy I think we know but to
a very small degree: and I doubt whether, with those faculties we
have, we shall ever be able to carry our general knowledge (I say not
particular experience) in this part much further. Experience is that
which in this part we must depend on. And it were to be wished that it
were more improved. We find the advantages some men's generous pains
have this way brought to the stock of natural knowledge. And if others,
especially the philosophers by fire, who pretend to it, had been so wary
in their observations, and sincere in their reports as those who call
themselves philosophers ought to have been, our acquaintance with the
bodies here about us, and our insight into their powers and operations
had been yet much greater.
17. Of the Powers that co-exist in Spirits yet narrower.
If we are at a loss in respect of the powers and operations of bodies, I
think it is easy to conclude we are much more in the dark in reference
to spirits; whereof we naturally have no ideas but what we draw from
that of our own, by reflecting on the operations of our own souls
within us, as far as they can come within our observation. But how
inconsiderable a rank the spirits that inhabit our bodies hold amongst
those various and possibly innumerable kinds of nobler beings; and how
far short they come of the endowments and perfections of cherubim and
seraphim, and infinite sorts of spirits above us, is what by a transient
hint in another place I have offered to my reader's consideration.
18. Thirdly, Of Relations between abstracted ideas it is not easy to say
how far our knowledge extends.
THIRDLY, As to the third sort of our knowledge, viz. the agreement or
disagreement of any of our ideas in any other relation: this, as it is
the largest field of our knowledge, so it is hard to determine how
far it may extend: because the advances that are made in this part of
knowledge, depending on our sagacity in finding intermediate ideas, that
may show the relations and habitudes of ideas whose co-existence is not
considered, it is a hard matter to tell when we are at an end of such
discoveries; and when reason has all the helps it is capable of, for the
finding of proofs, or examining the agreement or disagreement of remote
ideas. They that are ignorant of Algebra cannot imagine the wonders in
this kind are to be done by it: and what further improvements and helps
advantageous to other parts of knowledge the sagacious mind of man may
yet find out, it is not easy to determine. This at least I believe,
that the IDEAS OF QUANTITY are not those alone that are capable of
demonstration and knowledge; and that other, and perhaps more useful,
parts of contemplation, would afford us certainty, if vices, passions,
and domineering interest did not oppose or menace such endeavours.
Morality capable of Demonstration
The idea of a supreme Being, infinite in power, goodness, and wisdom,
whose workmanship we are, and on whom we depend; and the idea of
ourselves, as understanding, rational creatures, being such as are clear
in us, would, I suppose, if duly considered and pursued, afford such
foundations of our duty and rules of action as might place MORALITY
amongst the SCIENCES CAPABLE OF DEMONSTRATION: wherein I doubt not
but from self-evident propositions, by necessary consequences, as
incontestible as those in mathematics, the measures of right and wrong
might be made out, to any one that will apply himself with the same
indifferency and attention to the one as he does to the other of these
sciences. The RELATION of other MODES may certainly be perceived, as
well as those of number and extension: and I cannot see why they should
not also be capable of demonstration, if due methods were thought on to
examine or pursue their agreement or disagreement. 'Where there is no
property there is no injustice,' is a proposition as certain as any
demonstration in Euclid: for the idea of property being a right to
anything, and the idea of which the name 'injustice' is given being the
invasion or violation of that right, it is evident that these ideas,
being thus established, and these names annexed to them, I can as
certainly know this proposition to be true, as that a triangle has three
angles equal to two right ones. Again: 'No government allows absolute
liberty.' The idea of government being the establishment of society upon
certain rules or laws which require conformity to them; and the idea of
absolute liberty being for any one to do whatever he pleases; I am as
capable of being certain of the truth of this proposition as of any in
the mathematics.
19. Two things have made moral Ideas to be thought incapable of
Demonstration: their unfitness for sensible representation, and their
complexedness.
That which in this respect has given the advantage to the ideas
of quantity, and made them thought more capable of certainty and
demonstration, is,
First, That they can be set down and represented by sensible marks,
which have a greater and nearer correspondence with them than any words
or sounds whatsoever. Diagrams drawn on paper are copies of the ideas in
the mind, and not liable to the uncertainty that words carry in their
signification. An angle, circle, or square, drawn in lines, lies open to
the view, and cannot be mistaken: it remains unchangeable, and may at
leisure be considered and examined, and the demonstration be revised,
and all the parts of it may be gone over more than once, without any
danger of the least change in the ideas. This cannot be thus done in
moral ideas: we have no sensible marks that resemble them, whereby we
can set them down; we have nothing but words to express them by; which,
though when written they remain the same, yet the ideas they stand for
may change in the same man; and it is very seldom that they are not
different in different persons.
Secondly, Another thing that makes the greater difficulty in ethics is,
That moral ideas are commonly more complex than those of the
figures ordinarily considered in mathematics. From whence these two
inconveniences follow:--First, that their names are of more uncertain
signification, the precise collection of simple ideas they stand for
not being so easily agreed on; and so the sign that is used for them in
communication always, and in thinking often, does not steadily carry
with it the same idea. Upon which the same disorder, confusion, and
error follow, as would if a man, going to demonstrate something of an
heptagon, should, in the diagram he took to do it, leave out one of the
angles, or by oversight make the figure with one angle more than the
name ordinarily imported, or he intended it should when at first
he thought of his demonstration. This often happens, and is hardly
avoidable in very complex moral ideas, where the same name being
retained, one angle, i.e. one simple idea, is left out, or put in the
complex one (still called by the same name) more at one time than
another. Secondly, From the complexedness of these moral ideas there
follows another inconvenience, viz. that the mind cannot easily retain
those precise combinations so exactly and perfectly as is necessary in
the examination of the habitudes and correspondences, agreements or
disagreements, of several of them one with another; especially where it
is to be judged of by long deductions, and the intervention of several
other complex ideas to show the agreement or disagreement of two remote
ones.
The great help against this which mathematicians find in diagrams and
figures, which remain unalterable in their draughts, is very apparent,
and the memory would often have great difficulty otherwise to retain
them so exactly, whilst the mind went over the parts of them step by
step to examine their several correspondences. And though in casting up
a long sum either in addition, multiplication, or division, every part
be only a progression of the mind taking a view of its own ideas, and
considering their agreement or disagreement, and the resolution of
the question be nothing but the result of the whole, made up of such
particulars, whereof the mind has a clear perception: yet, without
setting down the several parts by marks, whose precise significations
are known, and by marks that last, and remain in view when the memory
had let them go, it would be almost impossible to carry so many
different ideas in the mind, without confounding or letting slip some
parts of the reckoning, and thereby making all our reasonings about it
useless. In which case the cyphers or marks help not the mind at all to
perceive the agreement of any two or more numbers, their equalities or
proportions; that the mind has only by intuition of its own ideas of
the numbers themselves. But the numerical characters are helps to
the memory, to record and retain the several ideas about which the
demonstration is made, whereby a man may know how far his intuitive
knowledge in surveying several of the particulars has proceeded; that so
he may without confusion go on to what is yet unknown; and at last have
in one view before him the result of all his perceptions and reasonings.
20. Remedies of our Difficulties in dealing demonstratively with moral
ideas.
One part of these disadvantages in moral ideas which has made them be
thought not capable of demonstration, may in a good measure be remedied
by definitions, setting down that collection of simple ideas, which
every term shall stand for; and then using the terms steadily and
constantly for that precise collection. And what methods algebra, or
something of that kind, may hereafter suggest, to remove the other
difficulties, it is not easy to foretell. Confident I am, that, if men
would in the same method, and with the same indifferency, search after
moral as they do mathematical truths, they would find them have a
stronger connexion one with another, and a more necessary consequence
from our clear and distinct ideas, and to come nearer perfect
demonstration than is commonly imagined. But much of this is not to
be expected, whilst the desire of esteem, riches, or power makes men
espouse the well-endowed opinions in fashion, and then seek arguments
either to make good their beauty, or varnish over and cover their
deformity. Nothing being so beautiful to the eye as truth is to the
mind; nothing so deformed and irreconcilable to the understanding as a
lie. For though many a man can with satisfaction enough own a no very
handsome wife in his bosom; yet who is bold enough openly to avow that
he has espoused a falsehood, and received into his breast so ugly a
thing as a lie? Whilst the parties of men cram their tenets down all
men's throats whom they can get into their power, without permitting
them to examine their truth or falsehood; and will not let truth have
fair play in the world, nor men the liberty to search after it; what
improvements can be expected of this kind? What greater light can be
hoped for in the moral sciences? The subject part of mankind in most
places might, instead thereof, with Egyptian bondage, expect Egyptian
darkness, were not the candle of the Lord set up by himself in men's
minds, which it is impossible for the breath or power of man wholly to
extinguish.
21. Fourthly, Of the three real Existences of which we have certain
knowledge.
FOURTHLY, As to the fourth sort of our knowledge, viz. of the REAL
ACTUAL EXISTENCE OF THINGS, we have an intuitive knowledge of OUR OWN
EXISTENCE, and a demonstrative knowledge of the existence of a GOD:
of the existence of ANYTHING ELSE, we have no other but a sensitive
knowledge; which extends not beyond the objects present to our senses.
22. Our Ignorance great.
Our knowledge being so narrow, as I have shown, it will perhaps give us
some light into the present state of our minds if we look a little into
the dark side, and take a view of OUR IGNORANCE; which, being infinitely
larger than our knowledge, may serve much to the quieting of disputes,
and improvement of useful knowledge; if, discovering how far we
have clear and distinct ideas, we confine our thoughts within the
contemplation of those things that are within the reach of our
understandings, and launch not out into that abyss of darkness, (where
we have not eyes to see, nor faculties to perceive anything), out of
a presumption that nothing is beyond our comprehension. But to be
satisfied of the folly of such a conceit, we need not go far. He that
knows anything, knows this, in the first place, that he need not seek
long for instances of his ignorance. The meanest and most obvious things
that come in our way have dark sides, that the quickest sight cannot
penetrate into. The clearest and most enlarged understandings of
thinking men find themselves puzzled and at a loss in every particle of
matter. We shall the less wonder to find it so, when we consider the
CAUSES OF OUR IGNORANCE; which, from what has been said, I suppose will
be found to be these three:--
First, Want of ideas. Its causes.
Secondly, Want of a discoverable connexion between the ideas we have.
Thirdly, Want of tracing and examining our ideas.
23. First, One Cause of our ignorance Want of Ideas.
I. Want of simple ideas that other creatures in other parts of the
universe may have.
FIRST, There are some things, and those not a few, that we are ignorant
of, for want of ideas.
First, all the simple ideas we have are confined (as I have shown) to
those we receive from corporeal objects by sensation, and from the
operations of our own minds as the objects of reflection. But how much
these few and narrow inlets are disproportionate to the vast whole
extent of all beings, will not be hard to persuade those who are not so
foolish as to think their span the measure of all things. What other
simple ideas it is possible the creatures in other parts of the universe
may have, by the assistance of senses and faculties more or perfecter
than we have, or different from ours, it is not for us to determine. But
to say or think there are no such, because we conceive nothing of them,
is no better an argument than if a blind man should be positive in it,
that there was no such thing as sight and colours, because he had no
manner of idea of any such thing, nor could by any means frame to
himself any notions about seeing. The ignorance and darkness that is in
us no more hinders nor confines the knowledge that is in others, than
the blindness of a mole is an argument against the quicksightedness of
an eagle. He that will consider the infinite power, wisdom, and goodness
of the Creator of all things will find reason to think it was not all
laid out upon so inconsiderable, mean, and impotent a creature as he
will find man to be; who in all probability is one of the lowest of
all intellectual beings. What faculties, therefore, other species of
creatures have to penetrate into the nature and inmost constitutions of
things; what ideas they may receive of them far different from ours, we
know not. This we know and certainly find, that we want several other
views of them besides those we have, to make discoveries of them more
perfect. And we may be convinced that the ideas we can attain to by
our faculties are very disproportionate to things themselves, when
a positive, clear, distinct one of substance itself, which is the
foundation of all the rest, is concealed from us. But want of ideas of
this kind, being a part as well as cause of our ignorance, cannot be
described. Only this I think I may confidently say of it, That the
intellectual and sensible world are in this perfectly alike: that that
part which we see of either of them holds no proportion with what we see
not; and whatsoever we can reach with our eyes or our thoughts of either
of them is but a point, almost nothing in comparison of the the rest.