EPISTEMOLOGY,
i-pis-ta->ol'a-je, is the philosophical examination of human knowledge. One
of the central problems that faces an epistemologist, a philosopher engaged in
the examination of knowledge, is how to refute the epistemological skeptic.
Such a skeptic should be clearly distinguished from an ontological skeptic. The
former claims that we have no knowledge of the
external
world, the past, the future, or the minds of others. The ontological skeptic, however, goes beyond
this-his skepticism is about whether anything exists other than himself. He has
doubts about whether there is a world or any mind external to himself, whether
anything happened before a few minutes ago, and whether anything will happen in
the future. The episteomlogical skeptic can consistently accept our usual
beliefs about past, present, and future. Knowledge, however, is more than mere
belief, and this skeptic's claim is that we lack knowledge about these things.
He
can, unlike the ontological skeptic, even be convinced that our usual common
sense beliefs are true, because, as Plato points out in his Socratic dialogue
Theaetetus, knowledge is more than true judgement or belief. Often we have
beliefs that luckily turn out to be true, but knowledge requires more than good
luck. Socrates' example about lawyers in the Theaetetus shows this. A lawyer
who is a skillful orator can persuade a jury to believe his client innocent
merely by the skill of his speech. Sometimes it is indeed true that the
defendant is innocent, and so the jurors, by luck, have true beliefs but
certainly not knowledge. Consider another example of two people who believe
there will be an eclipse on a certain day. Their beliefs turn out to be true,
but the first person holds the belief because he dreamed the eclipse was going
to occur, while the other believed it on the basis of precise astronomical
measurements. While both people have true beliefs, only the second could be
said to have knowledge. The epistemological skeptic holds that all our beliefs
are like those of the first person.
Some are true, but which are true is a matter of luck rather than
knowledge.
It seems, then, that besides true belief we
must have sound evidence or reason for our belief to obtain knowledge, That is,
knowledge is justified true belief. In this way lucky true beliefs would not
qualify as knowledge. But we still have not done enough to discover what is
needed for knowledge beyond true belief. To see that more is needed, consider
the example of someone who every day for years has seen a painting of his
mother on the wall of her living room. He enters the room again one day and on
looking at the wall believes, among other things, that the picture is still in
the living room. He is surely justified in this belief, but what is on the wall
is a very realistic photograph of the original painting, which has been hidden
behind a table in a corner of the room. Thus he has a justified true belief
about the painting's being in the room, but lacks knowledge. Again, it is
merely luck that his belief is true. Unfortunately, after many attempts by many
persons, no one has yet uncovered the needed fourth condition to add to
justified true belief to reach knowledge. How leniently or strictly the fourth
condition is construed has important consequences for the skeptic.Indeed, one
thing we shall try to discover as we proceed is just how lenient he can be and
still justify his thesis.
Consider first a very strict view of what is
needed for knowledge beyond justified true belief. It might well be that a
belief must be evident or certain or indubitable to be knowledge. But if this
is so, then a skeptic can argue that no evidence for beliefs about the external
world, the past, the future, and other minds is sufficient for certainty, and
thus there is no knowledge of these. And if there is no such knowledge, then
each person is limited to knowledge of himself and his own present sensations
and thoughts. This does not lead to
solipsism, which is the view that only I and my own thoughts and sensations
exist, but instead leads to the view that I only have knowledge of myself and my own sensations and thoughts.
DESCARTES
METHOD OF DOUBT
We can see this skeptic's point by turning to
the work of Rene Descartes, who employed what he called "the method of
doubt" in order to
establish
an indubitable or certain foundation of knowledge. It was his opinion that all
previous systems of knowledge were seriously deficient because they neither
required that the evidential basis of knowledge be certain nor provided a way
to extend certainty beyond the initial evidential base. As what is taken to be
knowledge is extended from the initial base to include more and more about
increasingly complex matters, no knowledge claim is better justified than the
evidential foundation of all knowledge. But if the foundational evidence is not
certain, then it can be false and the whole structure of knowledge claims
erected upon it can also be incorrect. Without certainty at its base and
without some way to extend certainty to other more rarified areas, the
cooperative, continuous human endeavor to extend the frontiers of knowledge
might be completely misguided because it would then continually lead to
falsehoods.
Descartes employed his method of doubt to find
what is initially or noninferentially indubitable or certain, and then proposed
that knowledge be extended by deductive inference because deduction preserves
certainty. His method of doubt is basically, to doubt everything that there is
some reason, however minimal, to doubt. Thus, if a situation possibly will
occur, and if it were to occur there would be some reason to doubt some
knowledge claim, then that claim is not noninferentially certain and it is not
to be part of the foundation. Let us apply this method of doubt to the four
kinds of claims that our skeptic denies are known.
First we claim to know much about the world
around us, at least at the times we seem to see hear feel taste and smell
various parts of it. We surely seem to see flowers, touch paper, hear music,
taste sugar, and smell perfume. At the very least, each of us is sure that he
perceives parts of his own body. Consequently, we claim to have perceptual
knowledge of our own bodies and the external world. However, by using
Descartes' method of doubt the skeptic can show that no perceptual claim is
initially or noninferentially certain because there is always some reason to
doubt it. It is possible that, even when I seem to be seeing my own hand
directly in front of my face, it is lying by my side; I am sleeping and
dreaming that I see my hand. Further, may seem I awake when, in fact I merely dream
I awake. The point is not that all my
experiences may forever he really dreams, but only that for each one it is
possible it is a dream. Thus while some experiences may be true perceptions of
the external world, none is immune from doubt. Those I feel most sure about may
be among those about which I am mistaken. Feeling sure is no guarantee of
either indubitability or truth. No claims about the external world are
initially certain.
Descartes argues, however, that some claims
about the present are initially indubitable. While it is possible there are
situations, such as dreaming, that would make it reasonable to doubt that I see
my hand, there is no possible situation that would justify my doubting that I
am doubting, or that it seems to me I see a hand, or that I, who seem to see a
hand, exist. Thus, even if I am always mistaken about the external world, it is
initially indubitable for me that I, who am mistaken, exist and that I have
experiences and beliefs. Furthermore, it is initially certain that I have
feelings such as pains and tickles and sensations of touch and taste. While my
beliefs may be mistaken, and I may misconstrue what causes my feelings and
sensations, it is indubitable that I have them at the same time I seem to have
them. Here, then, are some claims each person can place in the category of what
is initially certain for him.
Second, after I have had a belief, feeling, or
sensation, my memory can be mistaken about it, and so any of my attempts to
remember a belief, feeling, or sensation may lead me astray. I can always be
mistaken about what is not present and manifest to me now. As Bertrand Russell
pointed out, it is possible that the world was created just five minutes ago
and that everything at that time was just as we remember it now. It is possible
each person came into existence at that time with a bodily state that seems to
result from his existing before five minutes ago and with all his seemingly
correct but actually mistaken memories of a past before five minutes ago. This
is a possible situation, and if it occurred this situation would make knowledge
claims about the past incorrect. For this reason, no claims about the past are
noninferentially or initially certain.
Third, the situation is no,better for claims
about the future. No belief about the future is certain unless it is based on
some previous evidence. My beliefs that the sun will rise tomorrow and that I
will die some day are as close to certainty as any claims about the future, but
even if they are certain they are at most inferentially certain. That is,
knowledge of the future depends on
being inferred from some previous evidence. If I were the only living thing
ever on the earth and had never seen the light of day until just yesterday, it
would not be at all reasonable for me to believe that the sun will rise
tomorrow or that I will die some day. It is only the vast accumulation of past
evidence that makes some beliefs about the future even approach indubitability.
Fourth, beliefs about the minds of others face
a similar problem. It is possible that I am dreaming or hallucinating when I
seem to see some one else who is behaving in a way that leads me to believe
that he is in pain, or is thinking, or feeling some emotion, But even if I were
to know I was not dreaming or hallucinating, it is still possible that he is
feigning, that he expresses his inner, mental life in behavior quite different
from the way I express my own, of that what I see is not a man but a skillfully
made automaton.
Thus the skeptic can conclude that no claims
about the external world, the past, the future, or other minds are
noninferentially or initially indubitable or certain. While this establishes
one point he needs to justify his thesis, more is needed because it may be that
some initially indubitable claims can be used as ultimate reasons to extend
knowledge to the areas of initial dubitability. Indeed, though Descartes agreed
that all initially indubitable knowledge of what exists or occurs is limited to
those beliefs each man has about himself, and his own unique beliefs, feelings,
and sensations, Descartes thought he could avoid skepticism by providing a way
to extend knowledge from this very limited base.
DEDUCTION AND
THE EXTENSION OF CERTAINTY
Any extension of knowledge from the ultimate
evidential base involves inference, and if knowledge requires that we preserve
not only truth but also certainty, we must use only deductive inferences.
Basically, this is Descartes' full method: begin with certainty and extend
knowledge by a method of inference that guarantees to extend certainty. There
are, however, problems here that also play into the skeptic's hands.
A deductive argument, in barest form, consists
of statements, one of which is the conclusion and the others of which are the
premises. The premises are used to justify or provide evidence or reasons for
the conclusion. The purpose of a deductive argument is to establish two
relationships. The first is between the premises and the world-that is, they
should be true of the world. The second is a relationship between the premises
and the conclusion whereby it is necessary that if the premises are true then
the conclusion is true. When the latter relationship is established the
argument is valid. And when the premises are also true, the argument is sound
because the two relationships together guarantee the truth of the conclusion
and thus extend truth. Furthermore, if all the premises are certain, then so is
the conclusion.
The question is whether there are valid
arguments where the premises are noninferentially certain, and the conclusions,
although not initially certain, obtain inferential certainty through the
arguments. If we can find such arguments we will have extended certainty,
truth, and knowledge as Descartes hoped to do. There is, however, an immediate
problem. Generally, deductive arguments lead to conclusions that are implicit
in the premises and thus seem unsuited for any important extension of
knowledge. If we limit the premises to those that are only about one
individual's beliefs and immediate sensory experience, it would seem that no
conclusions about the past, future, external world, and other minds would be
deducible.
However, we can try, as Descartes did, to find
some general principles that relate beliefs and sensations to external objects,
other times, and minds, and that are initially certain. Such principles would
be conceptual truths that differ in important ways from statements that assert
the existence of particular things distinct from a person and his own experiences.
For example, compare the general statements that all bachelors are unmarried
with one that all bachelors are unhappy. Both are general because they mention
all entities of a certain sort. However, while the first can be known to be
true a priori-that is, known independently of any experiential or empirical
evidence-the second requires an empirical investigation of actual bachelors to
discover whether any are happy. The second, then, is known at best a
posteriori. It is dependent upon empirical evidence gathered from observation
or experimentation. The first is known once the concepts of being a bachelor
and being married are understood, and this knowledge is noninferetially certain
because it need not be based on or inferred from any other knowledge or
evidence. We can, then, expand the list of our ultimate, or initially certain
premises to contain a priori conceptual truths, including many with terms such
as "bachelor" and "unhappy" that do not refer merely to one
person or his thoughts and sensations.
There are still problems, however, because each
person needs conceptual truths relating himself and his own experience to other
places, minds and times. The problem can be illustrated by concentrating on
extending knowledge from the Cartesian base to the present external world. We
want general conceptual truths that relate persons, beliefs, and sensations to
the existence of external objects in such a way that each of us can use
additional premises about himself and his own experiences to deduce validly something
about the existence of external physical objects. In order to do this we must
take into account the ways experiences can mislead us about the external world.
The sense experience of someone who is under the influence of alcohol or drugs
is not a guide to the existence of external objects. The same is true of
abnormal conditions such as optical illusions which can result from special
lighting conditions and unusual relationships among objects However, there are
general conceptual principles that are noninferentially certain nd that relate
sense experience to external objects, such as the first premise in the
following argument:
1. If a normal perceiver, under normal
conditions, were to have an experience of a red object, then he would perceive
a red object (and so there would be a red object).
2. I now have an experience of a red object.
3. The relevant conditions and I are normal
now. Therefore
4. I now perceive a red object (and so there is
a red object now).
This is a valid argument, and let us agree that
the first principle is initially certain. But while it is also initially
certain for me that I am now having an experience of a red object, it is far
from certain, let alone initially certain, that the relevant conditions and I,
or anyone else, are normal at any particular time. Thus the third premise is
not part of the Cartesian base of knowledge and cannot be used to extend
knowledge from the base.
This illustrates the general problem. Any sound
deductive inference from indubitable statements about some person's sense
experience and indubitable general truths to conclusions about the existence of
external physical objects requires some premise about the person who has the
sense experience and the conditions in which he has them if the inference from
the particular sense experience he has to the existence of enteral objects is
to be valid. But none of these additional premises about people and conditions
are either initially certain general principles or statements merely about one
person's sense experience. Thus they are not part of the Cartesian base.
Similar problems arise for the three other
cases. Concerning the past, there are two different sorts of knowledge claims.
One kind is a present Memory claim about a past event, and one is about
something not presently remembered but about which there is supposedly present
evidence. The problem facing memory claims is that someone's believing that he
remembers something is not enough to guarantee correctness of memory, even if
it is only a claim about some inner experience he has had, such as an
experience of pain. In addition, it is more difficult to find an indubitable
general principle to link the present belief about the past with what actually
occurred. There is no analogue to normal observers and conditions for
remembering.
Where a claim about the past is not based on
memory it must be justified by testimony of others, relics and documents from
the past, or scientific theories that
have implications about the past. For example, someone can examine the pigment
of a painting to date its past origin, or use a theory about decay of radioactive particles to determine
the age of certain material. However, these means of obtaining knowledge of the
past depend on present perception of external objects. If, as previously
argued, we cannot extend certainty to claims about present external objects, we
cannot extend it beyond them to implications of present testimony, relics,
documents, and scientific theories for the past. But even if we could reach
inferential certainty about the present facts, additional general principles
are needed to obtain certainty about the past. Again, however, none of the
needed principles is initially indubitable. No statement relating the past
to present pigments, radioactive
material, testimony, or documents is initially certain. Each is at most
probably true relative to present empirical evidence, and thus it is not a
conceptual or a priori truth.
The same problems arise for extending certainty
to claims about the future and other minds. Claims about both of these would
obtain certainty only by inference from indubitable claims about the present.
But for other minds the relevant claims about the present concern presently
observed behavior, such as screaming or writhing. For the future, present
claims with implications for the future are needed. These can be general
principles, such as the claim that night follows day, or particular statements,
such as the claim that this piece of radioactive material will become lead in
so many years. But there is no initial certainty about any of these claims
because each depends on present observations of the external world. As with the
past, we have found no way to extend certainty to specific claims about present
observations, let alone extend it from them to claims that go beyond present
observations by implying something about the future.
An epistemological skeptic can use Descartes'
method of doubt to show that initial certainty accrues only to certain
conceptual principles and to each person's present claims about his own
existence, beliefs, sensations, and feelings. The skeptic can also show that
Descartes' method of extending certainty and knowledge from this base-the
method of deductive inference-does not succeed. For many skeptics this is
enough to establish their thesis, but others, such as David Hume, wish to go
even further. Hume, contradicting Descartes, claimed that no one has knowledge
about himself as something over and above his own sensations and ideas. Hume
claimed that whenever he introspected to discover or experience himself, he
always "stumbled on" some particular ideas or perceptions, and so he
never found anything distinct from them. For Hume, then, there is initial
certainty only about ideas and sensations. Any other knowledge, even about
oneself, involves inference from ideas. And, as with all the other cases, some
of the premises needed to link claims about presently perceived ideas to claims
about the nature of perceivers are far from initially certain. If Hume is
right, we are driven to a most radical skepticism, which leaves as knowledge
only claims about certain
ideas.
SKEPTICISM,
PROBABILITY, AND INDUCTION
All the skeptical conclusions we have reached
depend on two assumptions: that there must be ultimate, noninferentially
certain, evidence for empirical knowledge and that knowledge is extended from
this base only by extending certainty. This double requirement of certainty
gain plausibility because it may well be that indubitability must be added to
justified true belief to obtain knowledge. Then, given the restriction of noninferential certainty to a Cartesian
base, and the extension of certainty only by deductive inference, the skeptic's
point is made. However, even if we grant the need for an indubitable base, the
claim that all knowledge requires certainty seems too strong. It seems that
knowledge is extended by induction as well as deduction, and induction does not
extend certainty but only provides probability. We shall find, however, that an
epistemological skeptic can succeed even if he allows inductive inferences from
the indubitable base to what is justified as merely probable.
An inductive argument differs from a deductive
argument in that, unlike a valid deductive argument, it is possible for its
premises to be true and its conclusion false. Thus justification by means of
induction guarantees neither certainty nor truth. Nevertheless, if inductive
arguments can be said to confirm or support claims to a degree that makes them
probable, then perhaps such arguments
can be used to extend knowledge. In general, induction is used to make
inferences from a number of individual observed cases to universal or
statistical laws, or to individual unobserved cases. For example, from the
claim that observed changes in temperatures of gases vary with changes in the volume
and the pressure of the gas, we can inductively infer the perfect-gas law. This
states that the temperature of a gas is proportional to the product of the
pressure and volume of the gas. We can also infer the prediction that the next
gas to be examined will have the same relationship between its temperature and
its volume and pressure. And from the claim that 45% of an observed sample of
American voters favor a certain candidate for president, we can infer that probably the candidate will
receive about 45% of the actual vote. In each case the argument is from an
observed sample some group to a claim about the whole group or about some
member of the group that
has
not been observed.
The question at this point is whether a person
can start with his Cartesian base of indubitable knowledge and extend knowledge
probabilistically by inductive inferences so that it includes claims about a present external object, about
another persons beliefs, feelings, or sensations, about the past, or about the
future. Again, the easiest case seems to be that of a presently existing
external object, because we need only find something to make it probable that
someone is perceiving such an object. We need some set of indubitable
statements about observations, which can be used to infer inductively that
someone is perceiving an external object. For example, can we inductively
justify that someone is perceiving a cherry from the fact that he is having a
visual experience of something small, round, red, smooth, and plump, and then a
taste sensation of something tart? I might try to do this in my own case by
using the following argument:
1. All (most) times when I have had sensations
of something small, round, and so forth are times when I have perceived a
cherry.
2. 1 am having such sensations now.
Therefore, probabLy
3 . I am perceiving a cherry now.
We can grant that the second premise is
initially certain. However, the first premise is not certain because it is
clearly possible that some, even most of my previous experiences occurred while
dreamt or had hallucinations. Furthermore, if the first premise is supposed to
be based on past observations, it requires remembering or correctly recording a
significant number of past instances. As we have already seen, claims about the
past are not initially certain. Thus knowledge of the present external world is
not to be obtained in this way.
The consequences of this for our to know
something of the past, the future, and other minds is also disastrous. Without
knowledge the resent we cannot get knowledge of other minds or the past, and
without knowledge of the
present
and past, there is no knowledge of the future. No claim relating my present
sensations or beliefs to the past or to mental facts about others is initially
certain. We might try the premise that most times when I believe I remember
something are times I correctly remember it, or the premise that most times I
have a sensation of someone screaming in pain are times someone really is in
pain. While it surely seems that both premises are reasonable, they are not
initially nor noninferentially certain. Thus neither premise nor, it seems, any
other that would warrant the desired
inductive inference-can be ultimate premises in an indudictive argument to
extend knowledge from a Cartesian base. Consequently, neither deduction alone
nor the addition induction provides a way to extend probailistic knowledge, let
alone certain knowledge, from the base. Epistemological skepticism is still
secure
SKEPTICISM
AND THE INITIALLY REASONABLE
In our attempt to avoid skeptical conclusions
we have rejected the requirement that knowledge requires indubitability, but
this relaxation is not enough. We
have, however, been implicitly making three other assumptions that can be questioned:
namely, that only the Cartesian base is noninferentially certain, that a
noninferential basis of knowledge must be certain, and that at most deduction
and the kinds of inductive inferences previously stated can provide inferential
justification sufficient for knowledge. Perhaps use can justify rejecting some
of these assumptions, and, if so, perhaps that will enable us to refute
skepticism.
The first assumption has been rejected by those
known as "common sense" philosophers, in particular, Thomas Reid
(1711-1796), and, more recently, G. E. Moore (1873-1958). According to those
philosophers, some statements about the external world are noninferentially
certain and thus can be used to extend knowledge. Moore claimed that when
someone confidently believes he sees his own hand in front of his face, it is
initially certain that he sees a hand, even granting that it is possible he is
mistaken. We have been equating initial epistemological certainty with
indubitability and that in turn with there being no possible situation that
would make the claim unreasonable. If Moore is right, this is too restrictive a
conception of initial certainty. Indeed, it might be argued, the mere
possibility of being unreasonable should not count against a claim being certain,
if there actually is no other claim more reasonable to believe. If a claim is
as reasonable as any other, then no more reasonable claim would be available to
justify its rejection, and rejection would never be justified. Such certainty
might seem to provide a sufficient basis for knowledge.
Unfortunately, for any claim someone makes that
implies that some external object exists, it seems there is always one that is
more reasonable, namely, that he believes the object exists. This statement is
from the Cartesian base, and even with our liberalization of the conception of
certainty we seem driven back to the core of indubitability. It might be
objected that use should relax our restrictions on certainty even more, but
instead of arguing that point, let us consider whether certainty is needed for
a noninferential basis of knowledge.
Surely a claim that one's own hand exists is
initially reasonable, even if not certain. Why can we not extend knowledge from
such a base? This at least lets us escape to the present, perceived external
world, and perhaps from there we can extend knowledge further. Of course, many
skeptics would reject this move, but before doing so they should see how much
their thesis would be affected. It is clear they would have to admit that there
is knowledge about some presently perceived and perhaps very recently perceived
external objects. However, they need not retract their views about unperceived
presently existing objects, other minds, the past, and the future.
Consider first unperceived presently existing
external objects. To show that the hand I just saw exists now when I do not
perceive it, we need an inductive argument with a premise such as:
Most objects exist at a time they are not
perceived if they have been perceived just before that time.
Similar premises are needed for knowledge of
the past, such as:
Most memories of past sunrises correspond to
actual sunrises.
The skeptic can grant that if use could compile
evidence for such premises from repeated particular observations in the
present, then we could use the premises to extend knowledge to the unperceived
present and past. However, no one can observe now that something previously
perceived exists now when it is not perceived, or that something has happened
in the past that corresponds to a present memory. Consequently, there is no way
to use these premises to extend knowledge from initially reasonable present
observations to the unobserved resent or past.
We have seen that knowledge of the future
depends on knowledge of the present and the past, and so without knowledge of
the past there is no knowledge of the future. However, with knowledge of the
past and induction we could get knowledge of the future. For example, if we
knew that the sun has risen every day for centuries, then we could infer that,
probably, the sun will rise tomorrow.
It might also seem that knowledge of other
minds awaits only knowledge of the past, but a special problem arises. Even
allowing induction and knowledge of the past, only the person who has a
sensation or thought can observe that it accompanies certain behavior of his
body. Thus no one can observe that most bodily writhing and screams have been
accompanied by feelings of pain, because his observations of others are
restricted to their behavior. The strongest claim he could verify by
observation is that his own
writhing
and screamings have been accompanied by pain. But as a skeptic can point out,
this is too weak a premise to justify inductively that unobserved pains of
others accompany similar bodily behavior. In general, observations, even
repeated observations, of only one entity, provide too weak a basis for
inductive justification of a claim about other entities. In the case of other
minds
we can do no better. Thus, even granting knowledge of presently perceived
external objects and the past, we cannot extend knowledge from the initial base
to other minds.
SKEPTICISM
AND INDIRECT JUSTIFICATION
Rejecting the first assumption of the Cartesian
method and two additional assumptions has resulted in such a minimal extension
of knowledge
that
an epistemological skeptic might well agree to their rejection. It is not
clear, however, that he can safely give up the last assumption, namely, that at
most deduction and the preceding forms of induction provide inferential
justification sufficient for knowledge. Insofar as there is justification of
scientific theories that explain what is observable by postulating unobservable
entities, such as atoms, electrons, and neutrons, there is a third form of
justification. The general statements of these theories are not deducible from
either noninferentially certain or initially reasonable statements about
particular observations. And they are not inductively derivable from such
statements, because there is no way to observe the behavior of some of the
postulated entities to justify the general statements inductively from
particular observations. For example, the observable relationship between the
temperature of a gas and its pressure and volume expressed in the perfect-gas
law is explained by the atomic theory of gases. This theory postulates that a
gas consists of atoms in motion that, as the gas temperature rises, hit the
sides of whatever contains the gas with higher velocities and thereby increase
the pressure on the container This theory is not justified by observing the particular
atoms in motion, but primarily by its explanatory and predictive power and its
capacity to be tested
experimentally by its observable consequences, such as increases in
pressure. This is, then, a method of justification that differs considerably
from the other two.
To defeat the skeptic we need justified
postulations that have implications about unobserved presently existing
external objects, other minds, the past, and the future. Scientific theories
are not only models for this kind of justification, but they also provide the
implications we want. The explanation of presently observed phenomena, such as
clicks on a Geiger counter, are explained as the results of radioactive decay
that has occurred over many years. This implies not only that certain events
have occurred over a long period of time in the past, but also that
unobservable events are happening now. Astronomical theories and laws that
explain presently observed
configurations
of astronomical bodies, also imply, given these present configurations, claims
about the future, such as precise predictions about
eclipses.
The case for knowledge of other minds is made
by turning to psychological theories where presently observed behavior is
explained by means of unconscious
beliefs or repressions, feelings of guilt or inferiority, desires for love or
attention, and sensations of pain or pleasure. These and many other scientific
claims about the past, future, and other minds are justified in this indirect
postulational way.
It is clear how the skeptic would reply. He has
been lenient in allowing us to include among our basic evidential statements
those that are merely
noninferentially reasonable and in allowing this to use induction to extend
knowledge from this base. Here, however his leniency ends As we shall see,
there is some doubt about whether inductive inference from observed instances
provides justification that is strong enough for knowledge, but even granting
that it does, the skeptic would argue that the indirect justification of
scientific theories is clearly not strong enough for knowledge. Many of the
fundamental statements of scientific theories are not generalizations
inductively derived from particular observations.In the case of atomic theory,
for example, no entities to which such statements apply are observable. With no
observed cases on which to rely, verification is scanty at best. It is true
that theories can be falsified by finding crucial predictions that fail, but to
withstand such falsification as it explains and predicts does little to
approach what is needed for knowledge.
Skeptical
DOUBTS ABOUT Induction
It is difficult to answer the skeptic at this
point, especially because the fourth condition of knowing remains undiscovered.
Will it require certainty or at least justification so strong that only
deductive inference can be used to extend knowledge? Some People working in
this area find themselves inclined more and more in this direction, or at least
toward a condition that would eliminate this third kind of justification. Some
have even argued for a condition that could require such a high degree of
probability for knowledge that in many cases induction would not provide: an
extension of knowledge. Further more, some skeptics would also claim that no
form
of induction should be used to extend knowledge, because, unlike deduction, no
way has been found to justify its inferences. This is the
view of Hume, whose skeptical conclusions about minds we have already seen.
Briefly, Hume's point is this. We cannot justify
the accepted form of inductive inference by showing that true premises in
arguments of these forms always lead to true conclusions, because sometimes
false conclusions result. For example, at one time there was an enormous amount
of evidence that made it highly
probable that all swans are white. When Australia was explored, however,
it was found that some swans are black. The most we can hope to show is that
these inductive forms lead from true premises to true conclusions most of the
time. But how are we to establish this? We might grant that these forms have
been mostly successful in the past, but even if we allow that as fully
justified, we cannot deduce that they will continue to be successful most of
the time Such a conclusion involves the future as well as the past, and we have
seen that no statement solely about the future is deducible from one
solely
about the past. We could add an additional premise that the future will
resemble the past in relevant respects, but that premise is not initially reasonable
and must also be justified in some way. However, it does not seem deducible
from initially reasonable premises, and we cannot justify it inductively from
past observation unless induction is justified independently. Thus unless some
other form of justification succeeds, the problem of justifying induction first
clearly enunciated by Hume, like the problem of defining knowledge, which dates
back to Plato, remains unsolved.
CONCLUSION
The consequences of these two unsolved problems
for our present concern are crucial. With out a justification of induction or
some alternative and without a clear understanding of the fourth condition for,
knowing, the epistemological skeptic remains both unrefuted and with many
arguments to bolster his views. If knowledge requires certainty or at least a
high degree of probability, and there is no way to justify some nonduductive
form of inference, then the epistemological skeptic will be able to show that
his
thesis
is more reasonable than that of his opponents. As a consequence, our usual
convictions about the external world, the past, the future, and other minds
will turn out to be not knowledge but merely strongly felt beliefs.
See also EMPIRICISM, LINGUISTIC ANALYSIS,
LOGIC; and other articles listed in the Index under Epistemology.