An Essay Concerning Humane Understanding Vol II Chapter XVI. - Of the Degrees of Assent
by John Locke
1. Our Assent ought to be regulated by the Grounds of Probability.
The grounds of probability we have laid down in the foregoing chapter:
as they are the foundations on which our ASSENT is built, so are they
also the measure whereby its several degrees are, or ought to be
regulated: only we are to take notice, that, whatever grounds of
probability there may be, they yet operate no further on the mind which
searches after truth, and endeavours to judge right, than they appear;
at least, in the first judgment or search that the mind makes. I
confess, in the opinions men have, and firmly stick to in the world,
their assent is not always from an actual view of the reasons that at
first prevailed with them: it being in many cases almost impossible, and
in most, very hard, even for those who have very admirable memories, to
retain all the proofs which, upon a due examination, made them embrace
that side of the question. It suffices that they have once with care
and fairness sifted the matter as far as they could; and that they have
searched into all the particulars, that they could imagine to give any
light to the question; and, with the best of their skill, cast up the
account upon the whole evidence: and thus, having once found on which
side the probability appeared to THEM, after as full and exact an
inquiry as they can make, they lay up the conclusion in their memories,
as a truth they have discovered; and for the future they remain
satisfied with the testimony of their memories, that this is the opinion
that, by the proofs they have once seen of it, deserves such a degree of
their assent as they afford it.
2. These can not always be actually in View; and then we must content
ourselves with the remembrance that we once saw ground for such a Degree
of Assent.
This is all that the greatest part of men are capable of doing, in
regulating their opinions and judgments; unless a man will exact of
them, either to retain distinctly in their memories all the proofs
concerning any probable truth, and that too, in the same order, and
regular deduction of consequences in which they have formerly placed
or seen them; which sometimes is enough to fill a large volume on one
single question: or else they must require a man, for every opinion that
he embraces, every day to examine the proofs: both which are impossible.
It is unavoidable, therefore, that the memory be relied on in the case,
and that men be persuaded of several opinions, whereof the proofs are
not actually in their thoughts; nay, which perhaps they are not able
actually to recall. Without this, the greatest part of men must be
either very sceptics; or change every moment, and yield themselves up
to whoever, having lately studied the question, offers them arguments,
which, for want of memory, they are not able presently to answer.
3. The ill consequence of this, if our former Judgments were not rightly
made.
I cannot but own, that men's sticking to their past judgment, and
adhering firmly to conclusions formerly made, is often the cause of
great obstinacy in error and mistake. But the fault is not that they
rely on their memories for what they have before well judged, but
because they judged before they had well examined. May we not find a
great number (not to say the greatest part) of men that think they have
formed right judgments of several matters; and that for no other reason,
but because they never thought otherwise? that themselves to have judged
right, only because they never questioned, never examined, their own
opinions? Which is indeed to think they judged right, because they never
judged at all. And yet these, of all men, hold their opinions with the
greatest stiffness; those being generally the most fierce and firm in
their tenets, who have least examined them. What we once KNOW, we are
certain is so: and we may be secure, that there are no latent proofs
undiscovered, which may overturn our knowledge, or bring it in doubt.
But, in matters of PROBABILITY, it is not in every case we can be sure
that we have all the particulars before us, that any way concern the
question; and that there is no evidence behind, and yet unseen, which
may cast the probability on the other side, and outweigh all that at
present seems to preponderate with us. Who almost is there that hath
the leisure, patience, and means to collect together all the proofs
concerning most of the opinions he has, so as safely to conclude that he
hath a clear and full view; and that there is no more to be alleged for
his better information? And yet we are forced to determine ourselves on
the one side or other. The conduct of our lives, and the management of
our great concerns, will not bear delay: for those depend, for the most
part, on the determination of our judgment in points wherein we are
not capable of certain and demonstrative knowledge, and wherein it is
necessary for us to embrace the one side or the other.
4. The right Use of it, mutual Charity and Forbearance, in a necessary
diversity of opinions.
Since, therefore, it is unavoidable to the greatest part of men, if not
all, to have several OPINIONS, without certain and indubitable proofs
of their truth; and it carries too great an imputation of ignorance,
lightness, or folly for men to quit and renounce their former tenets
presently upon the offer of an argument which they cannot immediately
answer, and show the insufficiency of: it would, methinks, become
all men to maintain peace, and the common offices of humanity, and
friendship, in the diversity of opinions; since we cannot reasonably
expect that any one should readily and obsequiously quit his own
opinion, and embrace ours, with a blind resignation to an authority
which the understanding of man acknowledges not. For however it may
often mistake, it can own no other guide but reason, nor blindly submit
to the will and dictates of another. If he you would bring over to your
sentiments be one that examines before he assents, you must give him
leave at his leisure to go over the account again, and, recalling what
is out of his mind, examine all the particulars, to see on which side
the advantage lies: and if he will not think our arguments of weight
enough to engage him anew in so much pains, it is but what we often do
ourselves in the like case; and we should take it amiss if others should
prescribe to us what points we should study. And if he be one who takes
his opinions upon trust, how can we imagine that he should renounce
those tenets which time and custom have so settled in his mind, that he
thinks them self-evident, and of an unquestionably certainty; or which
he takes to be impressions he has received from God himself, or from men
sent by him? How can we expect, I say, that opinions thus settled should
be given up to the arguments or authority of a stranger or adversary,
especially if there be any suspicion of interest or design, as there
never fails to be, where men find themselves ill-trusted? We should do
well to commiserate our mutual ignorance, and endeavour to remove it in
all the gentle and fair ways of information; and not instantly treat
others ill, as obstinate and perverse, because they will not renounce
their own, and receive our opinions, or at least those we would force
upon them, when it is more than probable that we are no less obstinate
in not embracing some of theirs. For where is the man that has
incontestable evidence of the truth of all that he holds, or of the
falsehood of all he condemns; or can say that he has examined to the
bottom all his own, or other men's opinions? The necessity of believing
without knowledge, nay often upon very slight grounds, in this fleeting
state of action and blindness we are in, should make us more busy and
careful to inform ourselves than constrain others. At least, those who
have not thoroughly examined to the bottom all their own tenets, must
confess they are unfit to prescribe to others; and are unreasonable in
imposing that as truth on other men's belief, which they themselves have
not searched into, nor weighed the arguments of probability, on which
they should receive or reject it. Those who have fairly and truly
examined, and are thereby got past doubt in all the doctrines they
profess and govern themselves by, would have a juster pretence to
require others to follow them: but these are so few in number, and find
so little reason to be magisterial in their opinions, that nothing
insolent and imperious is to be expected from them: and there is reason
to think, that, if men were better instructed themselves, they would be
less imposing on others.
5. Probability is either of sensible Matter of Fact, capable of human
testimony, or of what is beyond the evidence of our senses.
But to return to the grounds of assent, and the several degrees of it,
we are to take notice, that the propositions we receive upon inducements
of PROBABILITY are of TWO SORTS: either concerning some particular
existance, or, as it is usually termed, matter of fact, which, falling
under observation, is capable of human testimony; or else concerning
things, which being beyond the discovery of our senses, are not capable
of any such testimony.
6. Concerning the FIRST of these, viz. PARTICULAR MATTER OF FACT.
I. The concurrent Experience of ALL other Men with ours, produces
Assurance approaching to Knowledge.
Where any particular thing, consonant to the constant observation of
ourselves and others in the like case, comes attested by the concurrent
reports of all that mention it, we receive it as easily, and build as
firmly upon it, as if it were certain knowledge; and we reason and act
thereupon with as little doubt as if it were perfect demonstration.
Thus, if all Englishmen, who have occasion to mention it, should affirm
that it froze in England the last winter, or that there were swallows
seen there in the summer, I think a man could almost as little doubt of
it as that seven and four are eleven. The first, therefore, and HIGHEST
DEGREE OF PROBABILITY, is, when the general consent of all men, in all
ages, as far as it can be known, concurs with a man's constant and
never-failing experience in like cases, to confirm the truth of any
particular matter of fact attested by fair witnesses: such are all
the stated constitutions and properties of bodies, and the regular
proceedings of causes and effects in the ordinary course of nature. This
we call an argument from the nature of things themselves. For what our
own and other men's CONSTANT OBSERVATION has found always to be after
the same manner, that we with reason conclude to be the effect of
steady and regular causes; though they come not within the reach of our
knowledge. Thus, That fire warmed a man, made lead fluid, and changed
the colour or consistency in wood or charcoal; that iron sunk in
water, and swam in quicksilver: these and the like propositions about
particular facts, being agreeable to our constant experience, as often
as we have to do with these matters; and being generally spoke of (when
mentioned by others) as things found constantly to be so, and therefore
not so much as controverted by anybody--we are put past doubt that a
relation affirming any such thing to have been, or any predication
that it will happen again in the same manner, is very true. These
PROBABILITIES rise so near to CERTAINTY, that they govern our thoughts
as absolutely, and influence all our actions as fully, as the most
evident demonstration; and in what concerns us we make little or
no difference between them and certain knowledge. Our belief, thus
grounded, rises to ASSURANCE.
7. II. Unquestionable Testimony, and our own Experience that a thing is
for the most part so, produce Confidence.
The NEXT DEGREE OF PROBABILITY is, when I find by my own experience, and
the agreement of all others that mention it, a thing to be for the most
part so, and that the particular instance of it is attested by many and
undoubted witnesses: v.g. history giving us such an account of men in
all ages, and my own experience, as far as I had an opportunity to
observe, confirming it, that most men prefer their private advantage to
the public: if all historians that write of Tiberius, say that Tiberius
did so, it is extremely probable. And in this case, our assent has a
sufficient foundation to raise itself to a degree which we may call
CONFIDENCE.
8. III. Fair Testimony, and the Nature of the Thing indifferent, produce
unavoidable Assent.
In things that happen indifferently, as that a bird should fly this or
that way; that it should thunder on a man's right or left hand, &c.,
when any particular matter of fact is vouched by the concurrent
testimony of unsuspected witnesses, there our assent is also
UNAVOIDABLE. Thus: that there is such a city in Italy as Rome: that
about one thousand seven hundred years ago, there lived in it a man,
called Julius Caesar; that he was a general, and that he won a battle
against another, called Pompey. This, though in the nature of the thing
there be nothing for nor against it, yet being related by historians of
credit, and contradicted by no one writer, a man cannot avoid believing
it, and can as little doubt of it as he does of the being and actions of
his own acquaintance, whereof he himself is a witness.
9. Experience and Testimonies clashing, infinitely vary the Degrees of
Probability.
Thus far the matter goes easy enough. Probability upon such grounds
carries so much evidence with it, that it naturally determines the
judgment, and leaves us as little liberty to believe or disbelieve, as a
demonstration does, whether we will know, or be ignorant. The difficulty
is, when testimonies contradict common experience, and the reports of
history and witnesses clash with the ordinary course of nature, or with
one another; there it is, where diligence, attention, and exactness are
required, to form a right judgment, and to proportion the assent to the
different evidence and probability of the thing: which rises and
falls, according as those two foundations of credibility, viz. COMMON
OBSERVATION IN LIKE CASES, and PARTICULAR TESTIMONIES IN THAT PARTICULAR
INSTANCE, favour or contradict it. These are liable to so great
variety of contrary observations, circumstances, reports, different
qualifications, tempers, designs, oversights, &c., of the reporters,
that it is impossible to reduce to precise rules the various degrees
wherein men give their assent. This only may be said in general, That
as the arguments and proofs PRO and CON, upon due examination, nicely
weighing every particular circumstance, shall to any one appear, upon
the whole matter, in a greater or less degree to preponderate on
either side; so they are fitted to produce in the mind such different
entertainments, as we call BELIEF, CONJECTURE, GUESS, DOUBT, WAVERING,
DISTRUST, DISBELIEF, &c.
10. Traditional Testimonies, the further removed the less their Proof
becomes.
This is what concerns assent in matters wherein testimony is made use
of: concerning which, I think, it may not be amiss to take notice of a
rule observed in the law of England; which is, That though the attested
copy of a record be good proof, yet the copy of a copy, ever so well
attested, and by ever so credible witnesses, will not be admitted as a
proof in judicature. This is so generally approved as reasonable,
and suited to the wisdom and caution to be used in our inquiry after
material truths, that I never yet heard of any one that blamed it.
This practice, if it be allowable in the decisions of right and wrong,
carries this observation along with it, viz. THAT ANY TESTIMONY, THE
FURTHER OFF IT IS FROM THE ORIGINAL TRUTH, THE LESS FORCE AND PROOF IT
HAS. The being and existence of the thing itself, is what I call the
original truth. A credible man vouching his knowledge of it is a good
proof; but if another equally credible do witness it from his report,
the testimony is weaker: and a third that attests the hearsay of an
hearsay is yet less considerable. So that in traditional truths, each
remove weakens the force of the proof: and the more hands the tradition
has successively passed through, the less strength and evidence does
it receive from them. This I thought necessary to be taken notice of:
because I find amongst some men the quite contrary commonly practised,
who look on opinions to gain force by growing older; and what a thousand
years since would not, to a rational man contemporary with the first
voucher, have appeared at all probable, is now urged as certain beyond
all question, only because several have since, from him, said it one
after another. Upon this ground propositions, evidently false or
doubtful enough in their first beginning, come, by an inverted rule of
probability, to pass for authentic truths; and those which found or
deserved little credit from the mouths of their first authors, are
thought to grow venerable by age, are urged as undeniable.
11. Yet History is of great Use.
I would not be thought here to lessen the credit and use of HISTORY: it
is all the light we have in many cases, and we receive from it a great
part of the useful truths we have, with a convincing evidence. I think
nothing more valuable than the records of antiquity: I wish we had more
of them, and more uncorrupted. But this truth itself forces me to say,
That no probability can rise higher than its first original. What has no
other evidence than the single testimony of one only witness must stand
or fall by his only testimony, whether good, bad, or indifferent; and
though cited afterwards by hundreds of others, one after another, is so
far from receiving any strength thereby, that it is only the weaker.
Passion, interest, inadvertency, mistake of his meaning, and a thousand
odd reasons, or capricios, men's minds are acted by, (impossible to
be discovered,) may make one man quote another man's words or meaning
wrong. He that has but ever so little examined the citations of writers,
cannot doubt how little credit the quotations deserve, where the
originals are wanting; and consequently how much less quotations of
quotations can be relied on. This is certain, that what in one age was
affirmed upon slight grounds, can never after come to be more valid in
future ages by being often repeated. But the further still it is from
the original, the less valid it is, and has always less force in the
mouth or writing of him that last made use of it than in his from whom
he received it.
12. Secondly, In things which Sense cannot discover, Analogy is the
great Rule of Probability.
[SECONDLY], The probabilities we have hitherto mentioned are only such
as concern matter of fact, and such things as are capable of observation
and testimony. There remains that other sort, concerning which men
entertain opinions with variety of assent, though THE THINGS BE SUCH,
THAT FALLING NOT UNDER THE REACH OF OUR SENSES, THEY ARE NOT CAPABLE OF
TESTIMONY. Such are, 1. The existence, nature and operations of finite
immaterial beings without us; as spirits, angels, devils, &c. Or the
existence of material beings which, either for their smallness in
themselves or remoteness from us, our senses cannot take notice of--as,
whether there be any plants, animals, and intelligent inhabitants in
the planets, and other mansions of the vast universe. 2. Concerning
the manner of operation in most parts of the works of nature: wherein,
though we see the sensible effects, yet their causes are unknown, and we
perceive not the ways and manner how they are produced. We see animals
are generated, nourished, and move; the loadstone draws iron; and the
parts of a candle, successively melting, turn into flame, and give us
both light and heat. These and the like effects we see and know: but the
causes that operate, and the manner they are produced in, we can only
guess and probably conjecture. For these and the like, coming not within
the scrutiny of human senses, cannot be examined by them, or be attested
by anybody; and therefore can appear more or less probable, only as they
more or less agree to truths that are established in our minds, and as
they hold proportion to other parts of our knowledge and observation.
ANALOGY in these matters is the only help we have, and it is from that
alone we draw all our grounds of probability. Thus, observing that the
bare rubbing of two bodies violently one upon another, produces heat,
and very often fire itself, we have reason to think, that what we call
HEAT and FIRE consists in a violent agitation of the imperceptible
minute parts of the burning matter. Observing likewise that the
different refractions of pellucid bodies produce in our eyes the
different appearances of several colours; and also, that the different
ranging and laying the superficial parts of several bodies, as of
velvet, watered silk, &c., does the like, we think it probable that
the COLOUR and shining of bodies is in them nothing but the different
arrangement and refraction of their minute and insensible parts. Thus,
finding in all parts of the creation, that fall under human observation,
that there is A GRADUAL CONNEXION OF ONE WITH ANOTHER, WITHOUT ANY GREAT
OR DISCERNIBLE GAPS BETWEEN, IN ALL THAT GREAT VARIETY OF THINGS WE SEE
IN THE WORLD, which are so closely linked together, that, in the several
ranks of beings, it is not easy to discover the bounds betwixt them; we
have reason to be persuaded that, BY SUCH GENTLE STEPS, things ascend
upwards in degrees of perfection. It is a hard matter to say where
sensible and rational begin, and where insensible and irrational end:
and who is there quick-sighted enough to determine precisely which is
the lowest species of living things, and which the first of those which
have no life? Things, as far as we can observe, lessen and augment, as
the quantity does in a regular cone; where, though there be a manifest
odds betwixt the bigness of the diameter at a remote distance, yet the
difference between the upper and under, where they touch one another, is
hardly discernible. The difference is exceeding great between some men
and some animals: but if we will compare the understanding and abilities
of some men and some brutes, we shall find so little difference, that it
will be hard to say, that that of the man is either clearer or larger.
Observing, I say, such gradual and gentle descents downwards in those
parts of the creation that are beneath man, the rule of analogy may make
it probable, that it is so also in things above us and our observation;
and that there are several ranks of intelligent beings, excelling us in
several degrees of perfection, ascending upwards towards the infinite
perfection of the Creator, by gentle steps and differences, that are
every one at no great distance from the next to it. This sort of
probability, which is the best conduct of rational experiments, and the
rise of hypothesis, has also its use and influence; and a wary reasoning
from analogy leads us often into the discovery of truths and useful
productions, which would otherwise lie concealed.
13. One Case where contrary Experience lessens not the Testimony.
Though the common experience and the ordinary course of things have
justly a mighty influence on the minds of men, to make them give or
refuse credit to anything proposed to their belief; yet there is one
case, wherein the strangeness of the fact lessens not the assent to
a fair testimony given of it. For where such supernatural events are
suitable to ends aimed at by Him who has the power to change the course
of nature, there, UNDER SUCH CIRCUMSTANCES, that may be the fitter to
procure belief, by how much the more they are beyond or contrary to
ordinary observation. This is the proper case of MIRACLES, which, well
attested, do not only find credit themselves, but give it also to other
truths, which need such confirmation.
14. The bare Testimony of Divine Revelation is the highest Certainty.
Besides those we have hitherto mentioned, there is one sort of
propositions that challenge the highest degree of our assent, upon bare
testimony, whether the thing proposed agree or disagree with common
experience, and the ordinary course of things, or no. The reason whereof
is, because the testimony is of such an one as cannot deceive nor be
deceived: and that is of God himself. This carries with it an assurance
beyond doubt, evidence beyond exception. This is called by a peculiar
name, REVELATION, and our assent to it, FAITH, which [as absolutely
determines our minds, and as perfectly excludes all wavering,] as our
knowledge itself; and we may as well doubt of our own being, as we can
whether any revelation from God be true. So that faith is a settled and
sure principle of assent and assurance, and leaves no manner of room
for doubt or hesitation. ONLY WE MUST BE SURE THAT IT BE A DIVINE
REVELATION, AND THAT WE UNDERSTAND IT RIGHT: else we shall expose
ourselves to all the extravagancy of enthusiasm, and all the error of
wrong principles, if we have faith and assurance in what is not DIVINE
revelation. And therefore, in those cases, our assent can be rationally
no higher than the evidence of its being a revelation, and that this is
the meaning of the expressions it is delivered in. If the evidence of
its being a revelation, or that this is its true sense, be only on
probable proofs, our assent can reach no higher than an assurance or
diffidence, arising from the more or less apparent probability of the
proofs. But of FAITH, and the precedency it ought to have before other
arguments of persuasion, I shall speak more hereafter; where I treat of
it as it is ordinarily placed, in contradistinction to reason; though in
truth it be nothing else but AN ASSENT FOUNDED ON THE HIGHEST REASON.
