11. Chapter XI
Of our Knowledge of the Existence of Other Things
1. Knowledge of the existence of other finite beings is to be had only by actual sensation.
The knowledge of our
own being we have by intuition. The existence of a God, reason clearly makes known to us, as has been shown.
The knowledge of the existence of any other thing we can have only by sensation: for there being no necessary
connexion of real existence with any idea a man hath in his memory; nor of any other existence but that of God
with the existence of any particular man: no particular man can know the existence of any other being, but only
when, by actual operating upon him, it makes itself perceived by him. For, the having the idea of anything in our
mind, no more proves the existence of that thing, than the picture of a man evidences his being in the world, or the
visions of a dream make thereby a true history.
2. Instance: whiteness of this paper.
It is therefore the actual receiving of ideas from without that gives us notice
of the existence of other things, and makes us know, that something doth exist at that time without us, which
causes that idea in us; though perhaps we neither know nor consider how it does it. For it takes not from the
certainty of our senses, and the ideas we receive by them, that we know not the manner wherein they are
produced: v.g. whilst I write this, I have, by the paper affecting my eyes, that idea produced in my mind, which,
whatever object causes, I call white; by which I know that that quality or accident (i.e., whose appearance before
my eyes always causes that idea) doth really exist, and hath a being without me. And of this, the greatest
assurance I can possibly have, and to which my faculties can attain, is the testimony of my eyes, which are the
proper and sole judges of this thing; whose testimony I have reason to rely on as so certain, that I can no more
doubt, whilst I write this, that I see white and black, and that something really exists that causes that sensation in
me, than that I write or move my hand; which is a certainty as great as human nature is capable of, concerning the
existence of anything, but a man's self alone, and of God.
3. This notice by our senses, though not so certain as demonstration, yet may be called knowledge, and proves the
existence of things without us.
The notice we have by our senses of the existing of things without us, though it be
not altogether so certain as our intuitive knowledge, or the deductions of our reason employed about the clear
abstract ideas of our own minds; yet it is an assurance that deserves the name of knowledge. If we persuade
ourselves that our faculties act and inform us right concerning the existence of those objects that affect them, it
cannot pass for an ill-grounded confidence: for I think nobody can, in earnest, be so sceptical as to be uncertain of
the existence of those things which he sees and feels. At least, he that can doubt so far, (whatever he may have
with his own thoughts,) will never have any controversy with me; since he can never be sure I say anything
contrary to his own opinion. As to myself, I think God has given me assurance enough of the existence of things
without me: since, by their different application, I can produce in myself both pleasure and pain, which is one
great concernment of my present state. This is certain: the confidence that our faculties do not herein deceive us,
is the greatest assurance we are capable of concerning the existence of material beings. For we cannot act
anything but by our faculties; nor talk of knowledge itself, but by the help of those faculties which are fitted to
apprehend even what knowledge is.
But besides the assurance we have from our senses themselves, that they do not err in the information they give us
of the existence of things without us, when they are affected by them, we are further confirmed in this assurance
by other concurrent reasons:--
4. Confirmed by concurrent reasons:--First, because we cannot have ideas of sensation but by the inlet of the
senses.
I. It is plain those perceptions are produced in us by exterior causes affecting our senses: because those that
want the organs of any sense, never can have the ideas belonging to that sense produced in their minds. This is too
evident to be doubted: and therefore we cannot but be assured that they come in by the organs of that sense, and
no other way. The organs themselves, it is plain, do not produce them: for then the eyes of a man in the dark
would produce colours, and his nose smell roses in the winter: but we see nobody gets the relish of a pineapple,
till he goes to the Indies, where it is, and tastes it.
5. Secondly, Because we find that an idea from actual sensation, and another from memory, are very distinct
perceptions.
II. Because sometimes I find that I cannot avoid the having those ideas produced in my mind. For
though, when my eyes are shut, or windows fast, I can at pleasure recall to my mind the ideas of light, or the sun,
which former sensations had lodged in my memory; so I can at pleasure lay by that idea, and take into my view
that of the smell of a rose, or taste of sugar. But, if I turn my eyes at noon towards the sun, I cannot avoid the
ideas which the light or sun then produces in me. So that there is a manifest difference between the ideas laid up
in my memory, (over which, if they were there only, I should have constantly the same power to dispose of them,
and lay them by at pleasure,) and those which force themselves upon me, and I cannot avoid having. And
therefore it must needs be some exterior cause, and the brisk acting of some objects without me, whose efficacy I
cannot resist, that produces those ideas in my mind, whether I will or no. Besides, there is nobody who doth not
perceive the difference in himself between contemplating the sun, as he hath the idea of it in his memory, and
actually looking upon it: of which two, his perception is so distinct, that few of his ideas are more distinguishable
one from another. And therefore he hath certain knowledge that they are not both memory, or the actions of his
mind, and fancies only within him; but that actual seeing hath a cause without.
6. Thirdly, because pleasure or pain, which accompanies actual sensation, accompanies not the returning of
those ideas without the external objects.
III. Add to this, that many of those ideas are produced in us with pain, which
afterwards we remember without the least offence. Thus, the pain of heat or cold, when the idea of it is revived in
our minds, gives us no disturbance; which, when felt, was very troublesome; and is again, when actually repeated:
which is occasioned by the disorder the external object causes in our bodies when applied to them: and we
remember the pains of hunger, thirst, or the headache, without any pain at all; which would either never disturb
us, or else constantly do it, as often as we thought of it, were there nothing more but ideas floating in our minds,
and appearances entertaining our fancies, without the real existence of things affecting us from abroad. The same
may be said of pleasure, accompanying several actual sensations. And though mathematical demonstration
depends not upon sense, yet the examining them by diagrams gives great credit to the evidence of our sight, and
seems to give it a certainty approaching to that of demonstration itself. For, it would be very strange, that a man
should allow it for an undeniable truth, that two angles of a figure, which he measures by lines and angles of a
diagram, should be bigger one than the other, and yet doubt of the existence of those lines and angles, which by
looking on he makes use of to measure that by.
7. Fourthly, because our senses assist one another's testimony of the existence of outward things, and enable
us to predict.
IV. Our senses in many cases bear witness to the truth of each other's report, concerning the existence of
sensible things without us. He that sees a fire, may, if he doubt whether it be anything more than a bare fancy, feel
it too; and be convinced, by putting his hand in it. Which certainly could never be put into such exquisite pain by
a bare idea or phantom, unless that the pain be a fancy too: which yet he cannot, when the burn is well, by raising
the idea of it, bring upon himself again.
Thus I see, whilst I write this, I can change the appearance of the paper; and by designing the letters, tell
beforehand what new idea it shall exhibit the very next moment, by barely drawing my pen over it: which will
neither appear (let me fancy as much as I will) if my hands stand still; or though I move my pen, if my eyes be
shut: nor, when those characters are once made on the paper, can I choose afterwards but see them as they are;
that is, have the ideas of such letters as I have made. Whence it is manifest, that they are not barely the sport and
play of my own imagination, when I find that the characters that were made at the pleasure of my own thoughts,
do not obey them; nor yet cease to be, whenever I shall fancy it, but continue to affect my senses constantly and
regularly, according to the figures I made them. To which if we will add, that the sight of those shall, from
another man, draw such sounds as I beforehand design they shall stand for, there will be little reason left to doubt
that those words I write do really exist without me, when they cause a long series of regular sounds to affect my
ears, which could not be the effect of my imagination, nor could my memory retain them in that order.
8. This certainty is as great as our condition needs.
But yet, if after all this any one will be so sceptical as to
distrust his senses, and to affirm that all we see and hear, feel and taste, think and do, during our whole being, is
but the series and deluding appearances of a long dream, whereof there is no reality; and therefore will question
the existence of all things, or our knowledge of anything: I must desire him to consider, that, if all be a dream,
then he doth but dream that he makes the question, and so it is not much matter that a waking man should answer
him. But yet, if he pleases, he may dream that I make him this answer, That the certainty of things existing in
rerum natura when we have the testimony of our senses for it is not only as great as our frame can attain to, but as
our condition needs. For, our faculties being suited not to the full extent of being, nor to a perfect, clear,
comprehensive knowledge of things free from all doubt and scruple; but to the preservation of us, in whom they
are; and accommodated to the use of life: they serve to our purpose wen enough, if they will but give us certain
notice of those things, which are convenient or inconvenient to us. For he that sees a candle burning, and hath
experimented the force of its flame by putting his finger in it, will little doubt that this is something existing
without him, which does him harm, and puts him to great pain; which is assurance enough, when no man requires
greater certainty to govern his actions by than what is as certain as his actions themselves. And if our dreamer
pleases to try whether the glowing heat of a glass furnace be barely a wandering imagination in a drowsy man's
fancy, by putting his hand into it, he may perhaps be wakened into a certainty greater than he could wish, that it is
something more than bare imagination. So that this evidence is as great as we can desire, being as certain to us as
our pleasure or pain, i.e., happiness or misery; beyond which we have no concernment, either of knowing or
being. Such an assurance of the existence of things without us is sufficient to direct us in the attaining the good
and avoiding the evil which is caused by them, which is the important concernment we have of being made
acquainted with them.
9. But reaches no further than actual sensation.
In fine, then, when our senses do actually convey into our
understandings any idea, we cannot but be satisfied that there doth something at that time really exist without us,
which doth affect our senses, and by them give notice of itself to our apprehensive faculties, and actually produce
that idea which we then perceive: and we cannot so far distrust their testimony, as to doubt that such collections of
simple ideas as we have observed by our senses to be united together, do really exist together. But this knowledge
extends as far as the present testimony of our senses, employed about particular objects that do then affect them,
and no further. For if I saw such a collection of simple ideas as is wont to be called man, existing together one
minute since, and am now alone, I cannot be certain that the same man exists now, since there is no necessary
connexion of his existence a minute since with his existence now: by a thousand ways he may cease to be, since I
had the testimony of my senses for his existence. And if I cannot be certain that the man I saw last to-day is now
in being, I can less be certain that he is so who hath been longer removed from my senses, and I have not seen
since yesterday, or since the last year: and much less can I be certain of the existence of men that I never saw.
And, therefore, though it be highly probable that millions of men do now exist, yet, whilst I am alone, writing this,
I have not that certainty of it which we strictly call knowledge; though the great likelihood of it puts me past
doubt, and it be reasonable for me to do several things upon the confidence that there are men (and men also of
my acquaintance, with whom I have to do) now in the world: but this is but probability, not knowledge.
10. Folly to expect demonstration in everything.
Whereby yet we may observe how foolish and vain a thing it is
for a man of a narrow knowledge, who having reason given him to judge of the different evidence and probability
of things, and to be swayed accordingly; how vain, I say, it is to expect demonstration and certainty in things not
capable of it; and refuse assent to very rational propositions, and act contrary to very plain and clear truths,
because they cannot be made out so evident, as to surmount every the least (I will not say reason, but) pretence of
doubting. He that, in the ordinary affairs of life, would admit of nothing but direct plain demonstration, would be
sure of nothing in this world, but of perishing quickly. The wholesomeness of his meat or drink would not give
him reason to venture on it: and I would fain know what it is he could do upon such grounds as are capable of no
doubt, no objection.
11. Past existence of other things is known by memory.
As when our senses are actually employed about any
object, we do know that it does exist; so by our memory we may be assured, that heretofore things that affected
our senses have existed. And thus we have knowledge of the past existence of several things, whereof our senses
having informed us, our memories still retain the ideas; and of this we are past all doubt, so long as we remember
well. But this knowledge also reaches no further than our senses have formerly assured us. Thus, seeing water at
this instant, it is an unquestionable truth to me that water doth exist: and remembering that I saw it yesterday, it
will also be always true, and as long as my memory retains it always an undoubted proposition to me, that water
did exist the 10th of July, 1688; as it will also be equally true that a certain number of very fine colours did exist,
which at the same time I saw upon a bubble of that water: but, being now quite out of sight both of the water and
bubbles too, it is no more certainly known to me that the water doth now exist, than that the bubbles or colours
therein do so: it being no more necessary that water should exist to-day, because it existed yesterday, than that the
colours or bubbles exist to-day, because they existed yesterday, though it be exceedingly much more probable;
because water hath been observed to continue long in existence, but bubbles, and the colours on them, quickly
cease to be.
12. The existence of other finite spirits not knowable, and rests on faith.
What ideas we have of spirits, and how
we come by them, I have already shown. But though we have those ideas in our minds, and know we have them
there, the having the ideas of spirits does not make us know that any such things do exist without us, or that there
are any finite spirits, or any other spiritual beings, but the Eternal God. We have ground from revelation, and
several other reasons, to believe with assurance that there are such creatures: but our senses not being able to
discover them, we want the means of knowing their particular existences. For we can no more know that there are
finite spirits really existing, by the idea we have of such beings in our minds, than by the ideas any one has of
fairies or centaurs, he can come to know that things answering those ideas do really exist.
And therefore concerning the existence of finite spirits, as well as several other things, we must content ourselves
with the evidence of faith; but universal, certain propositions concerning this matter are beyond our reach. For
however true it may be, v.g., that all the intelligent spirits that God ever created do still exist, yet it can never
make a part of our certain knowledge. These and the like propositions we may assent to, as highly probable, but
are not, I fear, in this state capable of knowing. We are not, then, to put others upon demonstrating, nor ourselves
upon search of universal certainty in all those matters; wherein we are not capable of any other knowledge, but
what our senses give us in this or that particular.
13. Only particular propositions concerning concrete existences are knowable.
By which it appears that there are
two sorts of propositions:--(1) There is one sort of propositions concerning the existence of anything answerable
to such an idea: as having the idea of an elephant, phoenix, motion, or an angel, in my mind, the first and natural
inquiry is, Whether such a thing does anywhere exist? And this knowledge is only of particulars. No existence of
anything without us, but only of God, can certainly be known further than our senses inform us. (2) There is
another sort of propositions, wherein is expressed the agreement or disagreement of our abstract ideas, and their
dependence on one another. Such propositions may be universal and certain. So, having the idea of God and
myself, of fear and obedience, I cannot but be sure that God is to be feared and obeyed by me: and this
proposition will be certain, concerning man in general, if I have made an abstract idea of such a species, whereof I
am one particular. But yet this proposition, how certain soever, that "men ought to fear and obey God" proves not
to me the existence of men in the world; but will be true of all such creatures, whenever they do exist: which
certainty of such general propositions depends on the agreement or disagreement to be discovered in those
abstract ideas.
14. And all general propositions that are known to be true concern abstract ideas.
In the former case, our
knowledge is the consequence of the existence of things, producing ideas in our minds by our senses: in the latter,
knowledge is the consequence of the ideas (be they what they will) that are in our minds, producing there general
certain propositions. Many of these are called aeternae veritates, and all of them indeed are so; not from being
written, all or any of them, in the minds of all men; or that they were any of them propositions in any one's mind,
till he, having got the abstract ideas, joined or separated them by affirmation or negation. But wheresoever we can
suppose such a creature as man is, endowed with such faculties, and thereby furnished with such ideas as we have,
we must conclude, he must needs, when he applies his thoughts to the consideration of his ideas, know the truth of
certain propositions that will arise from the agreement or disagreement which he will perceive in his own ideas.
Such propositions are therefore called eternal truths, not because they are eternal propositions actually formed,
and antecedent to the understanding that at any time makes them; nor because they are imprinted on the mind
from any patterns that are anywhere out of the mind, and existed before: but because, being once made about
abstract ideas, so as to be true, they will, whenever they can be supposed to be made again at any time, past or to
come, by a mind having those ideas, always actually be true. For names being supposed to stand perpetually for
the same ideas, and the same ideas having immutably the same habitudes one to another, propositions concerning
any abstract ideas that are once true must needs be eternal verities.