Anton Matyukhin





Международный Институт Экономики и Финансов, 1 курс,

Высшая школа экономики.





Epistemology as a discipline




Some Mental Activities Common to All Methods.

Observation and Experiment.

Analysis and Synthesis.

Imagination, Supposition and Idealisation.


Comparison and Analogy.


Inductive and deductive methods.

The Deductive-inductive Method.




Epistemology is one of the main branches of philosophy; its subject
matter concerns the nature, origin, scope, and limits of human
knowledge. The name is derived from the Greek terms episteme (knowledge)
and logos (theory), and accordingly this branch of philosophy is also
referred to as the theory of knowledge.

It is the branch of philosophy that investigates the basic nature of
knowledge, including its sources and validation. Epistemology is
concerned with the basic relationship between man’s mind and reality,
and with the basic operations of human reason. It therefore sets the
standards for the validation of all knowledge; it is the fundamental
arbiter of cognitive method.

Epistemology as a term in philosophy was probably first applied, by
J. F. Ferrier, to that department of thought whose subject matter is the
nature and validity of knowledge (Gr. epistimum, knowledge, and logos,
theory, account; Ger. Erkenntnistheorie). It is thus contrasted with
metaphysics, which considers the nature of reality, and with psychology,
which deals with the objective part of cognition, and, as Prof. James
Ward said, «is essentially genetic in its method.» Epistemology is
concerned rather with the possibility of knowledge in the abstract. In
the evolution of thought epistemological inquiry succeeded the
speculations of the early thinkers, who concerned themselves primarily
with attempts to explain existence. The differences of opinion, which
arose on this problem naturally, led to the inquiry as to whether any
universally valid statement was possible. The Sophists and the Sceptics,
Plato and Aristotle, the Stoics and the Epicureans took up the question
and from the time of Locke and Kant it has been prominent in modern
philosophy. It is extremely difficult, if not impossible, to draw a hard
and fast line between epistemology and other branches of philosophy. If,
for example, philosophy is divided into the theory of knowing and the
theory of being, it is impossible entirely to separate the latter
(Ontology) from the analysis of knowledge (Epistemology), so close is
the connection ‘between the two. Again, the relation between logic in
its widest sense and the theory of knowledge is extremely close. Some
thinkers have identified the two, while others regard Epistemology as a
subdivision of logic; others demarcate their relative spheres by
confining logic to the science of the laws of thought, i.e., to formal
logic. An attempt has been made by some philosophers to substitute
«Gnosiology» for «Epistemology» as a special term for that part of
Epistemology which is confined to «systematic analysis of the
conceptions employed by ordinary and scientific thought in interpreting
the world, and including an investigation of the art of knowledge, or
the nature of knowledge as such.» «Epistemology» would thus be reserved
for the broad questions of «the origin, nature and limits of knowledge».
The term Gnosiology has not come into general use.


Epistemological issues have been discussed throughout the history of
philosophy. Among the ancient Greeks, questions of knowledge were raised
by Plato and Aristotle, as well as by the Sophists and the Sceptics, and
many of the chief issues, positions and arguments were explored at this
time. In the systems of Plato and Aristotle, however, epistemological
questions were largely subordinated to metaphysical ones, and
epistemology did not emerge as a distinct area of inquiry.

The scholastics of the late medieval period were especially concerned
with two epistemological questions: the relationship between reason and
faith, and the nature of concepts and universals. The major positions on
the latter issue—realism, nominalism, and conceptualism—were defined
during this period.

The Reformation and the rise of modern science raised questions about
cognitive methodology, and gave rise to a rebirth of sceptical
doctrines, trends that culminated in the writings of Rene Descartes

During the modern period, from Descartes to Immanuel Kant
(1724-1804), epistemological concerns were at the forefront of
philosophy, as thinkers attempted to understand the implications of the
new science. They also attempted, unsuccessfully, to deal with sceptical
attacks on the validity of sense perception, concepts, and induction. In
the 19th and 20th centuries, epistemological issues continued to receive
attention from philosophers of various schools, including Idealism,
Logical Positivism, and Linguistic Analysis.

A familiarity with the history of philosophy provides the best
introduction to epistemology. The following works are of special
importance for epistemology:

Plato, Theaetetus

Aristotle, Posterior Analytics

Rene Descartes, Meditations

John Locke, Essay Concerning Human Understanding

David Hume, An Inquiry Concerning Human Understanding

Immanuel Kant, Prolegomena to Any Future Metaphysics

Epistemology as a discipline.

Why should there be such a subject as epistemology? Aristotle
provided the answer when he said that philosophy begins in wonder, in a
kind of puzzlement about things. Nearly all human beings wish to
comprehend the world they live in, a world that includes the individual
as well as other persons, and most people construct hypotheses of
varying degrees of sophistication to help them make sense of that world.
No conjectures would be necessary if the world were simple; but its
features and events defy easy explanation. The ordinary person is likely
to give up somewhere in the process of trying to develop a coherent
account of things and to rest content with whatever degree of
understanding he has managed to achieve.

Philosophers, in contrast, are struck by, even obsessed by, matters that
are not immediately comprehensible. Philosophers are, of course,
ordinary persons in all respects except perhaps one. They aim to
construct theories about the world and its inhabitants that are
consistent, synoptic, true to the facts and that possess explanatory
power. They thus carry the process of inquiry further than people
generally tend to do, and this is what saying that they have developed a
philosophy about these matters means. Epistemologists, in particular,
are philosophers whose theories deal with puzzles about the nature,
scope, and limits of human knowledge.

Like ordinary persons, epistemologists usually start from the assumption
that they have plenty of knowledge about the world and its multifarious
features. Yet, as they reflect upon what is presumably known,
epistemologists begin to discover that commonly accepted convictions are
less secure than originally assumed and that many of man’s firmest
beliefs are dubious or possibly even chimerical. Anomalous features of
the world that most people notice but tend to minimise or ignore cause
such doubts and hesitations. Epistemologists notice these things too,
but, in wondering about them, they come to realise that they provide
profound challenges to the knowledge claims that most individuals
blithely and unreflectingly accept as true.

What then are these puzzling issues? While there is a vast array of
anomalies and perplexities, two of these issues will be briefly
described in order to illustrate why such difficulties call into
question common claims to have knowledge about the world.


«Our knowledge of the external world».

Most people have noticed that vision can play tricks on them. A straight
stick put in water looks bent to them, but they know it is not; railroad
tracks are seen to be converging in the distance, yet one knows that
they are not; the wheels of wagons on a movie screen appear to be going
backward, but one knows that they are not; and the pages of
English-language books reflected in mirrors cannot be read from left to
right, yet one knows that they were printed to be read that way. Each of
these phenomena is thus misleading in some way. If human beings were to
accept the world as being exactly as it looks, they would be mistaken
about how things really are. They would think the stick in water really
to be bent, the railway tracks really to be convergent, and the writing
on pages really to be reversed. These are visual anomalies, and they
produce the sorts of epistemological disquietudes referred to above.
Though they may seem to the ordinary person to be simple problems, not
worth serious notice, for those who ponder them they pose difficult
questions. For instance, human beings claim to know that the stick is
not really bent and the tracks not really convergent. But how do they
know that these things are so?

Suppose one says that this is known because, when the stick is
removed from the water, one can see that it is not bent. But does seeing
a straight stick out of water provide a good reason for thinking that it
is not bent when seen in water? How does one know that, when the stick
is put into the water, it does not bend? Suppose one says that the
tracks do not really converge because the train passes over them at that
point. How does one know that the wheels on the train do not happen to
converge at that point? What justifies opposing some beliefs to others,
especially when all of them are based upon what is seen? One sees that
the stick in water is bent and also that the stick out of the water is
not bent. Why is the stick declared really to be straight; why in effect
is priority given to one perception over another?

One possible response to these queries is that vision is not
sufficient to give knowledge of how things are. One needs to correct
vision in some other way in order to arrive at the judgement that the
stick is really straight and not bent. Suppose a person asserts that his
reason for believing the stick in water is not bent is that he can feel
it with his hands to be straight when it is in the water. Feeling or
touching is a mode of sense perception, although different from vision.
What, however, justifies accepting one mode of perception as more
accurate than another? After all, there are good reasons for believing
that the tactile sense gives rise to misperception in just the way that
vision does. If a person chills one hand and warms the other, for
example, and inserts both into a tub of water having a uniform medium
temperature, the same water will feel warm to the cold hand and cold to
the warm hand. Thus, the tactile sense cannot be trusted either and
surely cannot by itself be counted on to resolve these difficulties.

Another possible response is that no mode of perception is sufficient to
guarantee that one can discover how things are. Thus, it might be
affirmed that one needs to correct all modes of perception by some other
form of awareness in order to arrive at the judgement, say, that the
stick is really straight. Perhaps that other way is the use of reason.
But why should reason be accepted as infallible? It also suffers from
various liabilities, such as forgetting, misestimating, or jumping to
conclusions. And why should one trust reason if its conclusions run
counter to those gained through perception, since it is obvious that
much of what is known about the world derives from perception?

Clearly there is a network of difficulties here, and one will have to
think hard in order to arrive at a clear and defensible explanation of
the apparently simple claim that the stick is really straight. A person
who accepts the challenge will, in effect, be developing a theory for
grappling with the famous problem called «our knowledge of the external
world.» That problem turns on two issues, namely, whether there is a
reality that exists independently of the individual’s perception of
it—in other words, if the evidence one has for the existence of
anything is what one perceives, how can one know that anything exists
unperceived?—and, second, how one can know what anything is really
like, if the perceptual evidence one has is conflicting.

The «other minds» problem.»

The second problem also involves seeing but in a somewhat unusual way.
It deals with that which one cannot see, namely the mind of another.
Suppose a woman is scheduled to have an operation on her right knee and
her surgeon tells her that when she wakes up she will feel a sharp pain
in her knee. When she wakes up, she does feel the pain the surgeon
alluded to. He can hear her groaning and see certain contortions on her
face. But he cannot feel what she is feeling. There is thus a sense in
which he cannot know what she knows. What he claims to know, he knows
because of what others who have undergone operations tell him they have
experienced. But, unless he has had a similar operation, he cannot know
what it is that she feels.

Indeed, the situation is still more complicated; for, even if the
doctor has had such a surgical intervention, he cannot know that what he
is feeling after his operation is exactly the same sensation that the
woman is feeling. Because each person’s sensation is private, the
surgeon cannot really know that what the woman is describing as a pain
and what he is describing as a pain are really the same thing. For all
he knows, she could be referring to a sensation that is wholly different
from the one to which he is alluding.

In short, though another person can perceive the physical
manifestations the woman exhibits, such as facial grimaces and various
sorts of behaviour, it seems that only she can have knowledge of the
contents of her mind. If this assessment of the situation is correct, it
follows that it is impossible for one person to know what is going on in
another person’s mind. One can conjecture that a person is experiencing
a certain sensation, but one cannot, in a strict sense of the term, know
it to be the case.

If this analysis is correct, one can conclude that each human being
is inevitably and even in principle cut off from having knowledge of the
mind of another. Most people, conditioned by the great advances of
modern technology, believe that in principle there is nothing in the
world of fact about which science cannot obtain knowledge. But the
«other-minds problem» suggests the contrary—namely, that there is a
whole domain of private human experience that is resistant to any sort
of external inquiry. Thus, one is faced with a profound puzzle, one of
whose implications is that there can never be a science of the human


These two problems resemble each other in certain ways and differ in
others, but both have important implications for epistemology.

First, as the divergent perceptions about the stick indicate, things
cannot just be, as they appear to be. People believe that the stick,
which looks bent when it is in the water, is really straight, and they
also believe that the stick, which looks straight when it is out of the
water, is really straight. But, if the belief that the stick in water is
really straight is correct, then it follows that the perception human
beings have when they see the stick in water cannot be correct. That
particular perception is misleading with respect to the real shape of
the stick. Hence, one has to conclude that things are not always, as
they appear to be.

It is possible to derive a similar conclusion with respect to the
mind of another. A person can exhibit all the signs of being in pain,
but he may not be. He may be pretending. On the basis of what can be
observed, it cannot be known with certitude that he is or that he is not
in pain. The way he appears to be may be misleading with respect to the
way he actually is. Once again vision can be misleading.

Both problems thus force one to distinguish between the way things
appear and the way they really are. This is the famous philosophical
distinction between appearance and reality. But, once that distinction
is drawn, profound difficulties arise about how to distinguish reality
from mere appearance. As will be shown, innumerable theories have been
presented by philosophers attempting to answer this question since time

Second, there is the question of what is meant by «knowledge.» People
claim to know that the stick is really straight even when it is
half-submerged in water. But, as indicated earlier, if this claim is
correct, then knowledge cannot simply be identical with perception. For
whatever theory about the nature of knowledge one develops, the theory
cannot have as a consequence that knowing something to be the case can
sometimes be mistaken or misleading.

Third, even if knowledge is not simply to be identified with
perception, there nevertheless must be some important relationship
between knowledge and perception. After all, how could one know that the
stick is really straight unless under some conditions it looked
straight? And sometimes a person who is in pain exhibits that pain by
his behaviour; thus there are conditions that genuinely involve the
behaviour of pain. But what are those conditions? It seems evident that
the knowledge that a stick is straight or that one is in great pain must
come from what is seen in certain circumstances: perception must somehow
be a fundamental element in the knowledge human beings have. It is
evident that one needs a theory to explain what the relationship is—and
a theory of this sort, as the history of the subject all too well
indicates, is extraordinarily difficult to develop.

The two problems also differ in certain respects. The problem of
man’s knowledge of the external world raises a unique difficulty that
some of the best philosophical minds of the 20th century (among them,
Bertrand Russell, H.H. Price, C.D. Broad, and G.E. Moore) spent their
careers trying to solve. The perplexity arises with respect to the
status of the entity one sees when one sees a bent stick in water. In
such a case, there exists an entity—a bent stick in water—that one
perceives and that appears to be exactly where the genuinely straight
stick is. But clearly it cannot be; for the entity that exists exactly
where the straight stick is is the stick itself, an entity that is not
bent. Thus, the question arises as to what kind of a thing this
bent-stick-in-water is and where it exists.

The responses to these questions have been innumerable, and nearly all
of them raise further difficulties. Some theorists have denied that what
one sees in such a case is an existent entity at all but have found it
difficult to explain why one seems to see such an entity. Still others
have suggested that the image seen in such a case is in one’s mind and
not really in space. But then what is it for something to be in one’s
mind, where in the mind is it, and why, if it is in the mind, does it
appear to be «out there,» in space where the stick is? And above all,
how does one decide these questions? The various questions posed above
only suggest the vast network of difficulties, and in order to
straighten out its tangles it becomes indispensable to develop theories.


In accordance with a proposal made above, epistemology, or the logic
of scientific discovery, -should be identified with the theory of
scientific method. The theory of method, in so far as it goes beyond the
purely logical analysis of the relations between scientific statements,
is concerned with the choice of methods—with decisions about the way in
which scientific statements are to be dealt with. These decisions will
of course depend in their turn upon the aim, which we choose from among
a number of possible aims.

Methodology or a scientific method is a collective term denoting the
various processes by the aid of which the sciences are built up. In a
wide sense, any mode of investigation by which scientific or other
impartial and systematic knowledge is acquired is called a scientific

What are the rules of scientific method, and why do we need them? Can
there be a theory of such rules, a methodology? The way in which one
answers these questions will largely depend upon one’s attitude to
science. The way in which one answers these questions will largely
depend upon one’s attitude to science. Those who, like the positivists,
see empirical science as a system of statements, which satisfy certain
logical criteria, such as meaningfulness or verifiability, will give
one-answer. A very different answer will be given by those who tend to
see the distinguishing characteristic of empirical statements in their
susceptibility to revision—in the fact that they can be criticised,-and
superseded by better ones; and who regard it as their task to analyse
the characteristic ability of science to advance, and the characteristic
manner in which a choice is made, in crucial cases, between conflicting
systems of theories.

Such methods, as it was mentioned above, are of two principal types—
technical and logical. A technical or technological method is a method
of manipulating the phenomena under investigation, measuring them with
precision, and determining the conditions under which they occur, so as
to be able to observe them in a favourable and fruitful manner. A
logical method is a method of reasoning about the phenomena
investigated, a method of drawing inferences from the conditions under
which they occur, so as to interpret them as accurately as possible. The
term «scientific method» in the first instance probably suggests to most
minds the technical methods of manipulation and measurement. These
technical methods are very numerous and they are different in the
different sciences. Few men ever master the technical methods of more
than one science or one group of closely connected sciences. An account
of the most important technical methods is usually given in connection
with the several sciences. It would be impossible, even if it were
desirable, to give a useful survey of all, or even of the most
important, technical methods of science. It is different with the
logical methods of science. These methods of reasoning from the
available evidence are not really numerous, and are essentially the same
in all the sciences. It is both possible and desirable to survey them in
outline. Moreover, these logical methods of science are in a very real
sense the soul of the technical methods.

In pure science the technical methods are not regarded as an end in
themselves, but merely as a means to the discovery of the nature of the
phenomena under investigation. This is done by drawing conclusions from
the observations and experiments, which the technical methods render
possible. Sometimes the technical methods make it possible for the
expert investigator to observe and measure certain phenomena, which
otherwise could either not be observed and measured at all, or not so
accurately. Sometimes they enable him so to determine the conditions of
their occurrence that he can draw reliable conclusions about them,
instead of having to be content with unverified conjectures. The highly
speculative, mainly conjectural character of early science was no doubt
due entirely to the lack of suitable technical methods and scientific
instruments. In a sense; therefore, it may be said that the technical
methods of science are auxiliary to the logical methods, or methods of
reasoning. And it is these methods that are to be considered in the
present article. The technical methods of science, as ought to be clear
from the preceding remarks, are of first rate importance, ‘and we have
not the remotest desire to underrate them; but it would be futile to
attempt to survey them here.

Some Mental Activities Common to All Methods.

There are certain mental activities, which are so absolutely
indispensable to science that they are practically always employed in
scientific investigations, however much these may vary in other
respects. In a wide sense these mental activities might consequently be
called methods of science, and they are frequently so called. But this
practice is objectionable, because it leads to cross division and
confusion. What is common to all methods should not itself be called a
method, for it only encourages the effacing of important differences;
and when there are many such factors common to all the methods, or most
of them, confusion is inevitable. When the mental activities involved
are more or less common to the methods, these must be differentiated by
reference to other, variable factors—such as the different types of data
from which the inferences are drawn, and the different types of order
sought or discovered in the different kinds, of phenomena investigated—
the two sets of differences being, of course, intimately connected. The
mental activities referred to are the following: Observation (including
experiment), analysis and synthesis, imagination, supposition and
idealisation, inference (inductive and deductive), and comparison
(including analogy). A few words must be said about each of these; but
no significance should be attached to the order in which they are dealt

Observation and Experiment.

Observation is the act of apprehending things and events, their
attributes and their concrete relationships. From the point of view of
scientific interest two types of observation may be distinguished,
namely: (1) The bare observation of phenomena under conditions which are
beyond the control of the investigator, and (2) experiment, that is, the
observation of phenomena under conditions controlled by the
investigator. What distinguishes experiment from bare observation is
control over what is observed, not the use of scientific apparatus, nor
the amount of trouble taken. The mere use of telescopes or microscopes,
etc., even the selection of specially suitable times and places of
observation, does not constitute an experiment, if there is no control
over the phenomenon observed. On the other hand, where there is such
control, there is experiment, even if next to no apparatus be used, and
the amount of trouble involved be negligible. The making of experiments
usually demands the employment of technical methods, but the main
interest centres in the observations made possible thereby. The great
advantage of experiment over bare observation is that it renders
possible a more reliable analysis of complex phenomena, and more
reliable inferences about their connections, by the variation of
circumstances, which it effects. Its importance is so great that people
commonly speak of «experimental method.» The objection to this is that
experiment may be, and is, used in connection with various methods,
which are differentiated on other, and more legitimate, grounds. To
speak of a method of observation is even less permissible, seeing that
no method can be employed without it.

Analysis and Synthesis.

The phenomena of nature are very complex and, to all appearances,
very confused. The discovery of any kind of order in them is only
rendered possible by processes of analysis and synthesis. These are as
essential to all scientific investigation as is observation itself. The
process of analysis is helped by the comparison of two or more objects
or events that are similar in some respects and different in others. But
while comparison is a necessary instrument of analysis, analysis, in its
turn, renders possible more exact comparison. After analysing some
complex whole into its parts or aspects, we may tentatively connect one
of these with another in order to discover a law of connection, or we
may, in imagination, combine again some of them and so form an idea of
what may be common to many objects or events, or to whole classes of
them. Some combinations so obtained may not correspond to anything that
has ever been observed. In this way analysis and synthesis, even though
they are merely mental in the first instance, prepare the way for
experiment, for discovery and invention.

Imagination, Supposition and Idealisation.

Such order as may be inherent in the phenomena of nature is not
obvious on the face of them. It has to be sought out by an active
interrogation of nature. The interrogation takes the form of making
tentative suppositions, with the aid of imagination, as to what kind of
order might prevail in the phenomena under investigation. Such
suppositions are usually known as hypotheses, and the formation of
fruitful hypotheses requires imagination and originality, as well as
familiarity with the facts investigated. Without the guidance of such
hypotheses observation itself would be barren in science for we should
not know what to look for. Mere staring at facts is not yet scientific
observation of them. Hence for science any hypothesis, provided it can
be put to the test of observation or experiment, is better than none.
For observation not guided by ideas is blind, just as ideas not tested
by observations are empty. Hypotheses that can be put to the test, even
if they should turn out to be false, are called «fruitful»; those that
cannot be so tested even if they should eventually be found to be true,
are for the time being called «barren.» Intimately connected with the
processes of imagination and supposition is the process of idealisation,
that is, the process of conceiving the ideal form or ideal limit of
something which may be observable but always falls short, in its
observed forms, of the ideal. The use of limiting cases in mathematics,
and of conceptions like those of an «economic man» in science are
examples of such idealisation.


This is the process of forming judgements or opinions on the ground
of other judgements or on the evidence of observation. The evidence may
be merely supposed for the sake of argument, or with a view to the
further consideration of the con-sequences, which follow from it. It is
not always easy to draw the line between direct observation and
inference. People, even trained people, do not always realise, e.g.,
when they pass from the observation of a number of facts to a
generalisation which, at best, can only be regarded as an inference from
them. But the difficulty need not be exaggerated. There are two
principal types of inference, namely deductive and inductive. Inductive
inference is the process of inferring some kind of order among phenomena
from observations made. Deductive inference is the process of applying
general truths or concepts to suitable instances. In science inductive
inference plays the most important role, and the methods of sciences are
mainly instruments of induction or auxiliaries thereto. But deductive
inference is also necessary to science, and is, in fact, a part of
nearly all complete inductive investigations. Still, marked inductive
ability is very rare. There are thousands who can more or less correctly
apply a discovery for one who can make it.

Comparison and Analogy.

Reference has already been made to the importance of the process of
comparison in the mental analysis of observed phenomena. The observation
of similarities and differences, aided by the processes of analysis and
synthesis, is one of the first steps to knowledge of every kind, and
continues to be indispensable to the pursuit of science throughout its
progress. But there are degrees of similarity. Things may be so alike
that they are at once treated as instances of the same kind or class.
And the formulation and application of generalisations of all kinds are
based upon this possibility of apprehending such class resemblances. On
the other hand, there is a likeness, which stops short of such close
class likeness. Such similarity is usually called analogy. The term is
applied to similarity of structure or of function or of relationship, in
fact, to similarity of almost every kind except that which characterises
members of the same class, in the strict sense of the term. And analogy
plays very important part in the work of science, especially in
suggesting those suppositions or hypotheses which, as already explained,
are so essential to scientific research and discovery.

After this brief survey of various mental activities which are more or
less involved in the pursuit of every kind of knowledge, and
consequently from no suitable bases for the differentiation of the
various methods of science, we may now proceed to the consideration of
the several scientific methods properly so called.


This may be described as the oldest and simplest of scientific
methods. The observation of similarities between certain things, and
classing them together, marks the earliest attempt to discover some kind
of order in the apparently chaotic jumble of things that confront the
human mind. Language bears witness to the vast number of classifications
made spontaneously by pre-scientific man. For every common noun
expresses the recognition of a class; and language is much older than
science. The first classifications subserved strictly practical
purposes, and had reference mainly to the uses which man could make of
the things classified. They were frequently also based on superficial
resemblances, which veiled deeper differences, or were influenced by
superficial differences, which diverted attention from deeper
similarities. But with the growth of the scientific spirit
classifications became more objective or more natural, attention being
paid to the objective nature of the things themselves rather than to
their human uses. Even now scientific classification rarely begins at
the beginning, but sets out from current classifications embodied in
language. It has frequent occasion to correct popular classifications.
At the same time it has difficulties of its own, and more than one
science has been held up for centuries for want of a really satisfactory
scheme or classification of the phenomena constituting its field of
investigation. To recognise a class is to recognise the unity of
essential attributes in a multiplicity of instances; it is a recognition
of the one in the many. To that extent it is a discovery of order in
things. And although it is the simplest method of science, and can be
applied before any other method, it is also the fundamental method,
inasmuch as its results are usually assumed when the other methods are
applied. For science is not, as a rule, concerned with individuals as
such, but with kinds or classes. This means that the investigator
usually assumes the accuracy of the classification of the phenomena,
which he is studying. Of course, this does not always turn out to be the
case. And the final outcome of the application of other methods of
science to certain kinds of phenomena may be a new classification of

Inductive and deductive methods.

Below is the summary of contrasts in the major tenets of inductivism and
of Popper’s deductivism.. I begin with a caricature of inductivism in
the form of eight theses:

1. Science strives for justified, proven knowledge, for certain truth.

2. All scientific inquiry begins with observations or experiments.

3. The observational or experimental data are organised into a
hypothesis, which is not yet proven (context of discovery).

4. The observations or experiments are repeated many times.

5. The greater the number of successful repetitions, the higher the
probability of the truth of the hypothesis (context of justification).

6. As soon as we are satisfied that we have reached certainty in that
manner we lay the issue aside forever as a proven law of nature.

7. We then turn to the next observation or experiment with which we
proceed in the same manner.

8. With the conjunction of all these proven theories we build the
edifice of justified and certain science.

In summary, the inductivist believes that science moves from the
particulars to the general and that the truth of the particular data is
transmitted to the general theory.

Now we will observe a caricature of Popper’s theory of deduc-tivism,
again in the form of eight theses:

1. Science strives for absolute and objective truth, but it can never
reach certainty.

2. All scientific inquiry begins with a rich context of background
knowledge and with the problems within this context and with
metaphysical research programmes.

3. A theory, that is, a hypothetical answer to a problem, is freely
invented within the metaphysical research programme: it explains the
observable by the unobservable.

4. Experimentally testable consequences, daring consequences that is,
are deduced from the theory and corresponding experiments are carried
out to test the predictions.

5. If an experimental result comes out as predicted, it is taken as a
value in itself and as an encouragement to continue with the theory, but
it is not taken as an element of proof of the theory of the

6. As soon as an experimental result comes out against the prediction
and we arc satisfied that it is not a blunder we decide to consider the
theory falsified, but only tentatively so.

7. With this we gain a deeper understanding of our problem and proceed
to invent our next hypothetical theory for solving it, which we treat
again in the same way.

8. The concatenation of all these conjectures and refutations
constitutes the dynamics of scientific progress, moving ever closer to
the truth, but never reaching certainty.

In summary, the Popperian deductivist believes that science moves
from the general to the particulars and back to the general— a process
without end. Let me inject a metaphor. I might liken the Popperian view
of science to that of a carriage with two horses. The experimental horse
is strong, but blind. The theoretical horse can see, but it cannot pull.
Only both together can bring the carriage forward. And behind it leaves
a track bearing witness to the incessant struggle of trial and error.

The Deductive-inductive Method.

Just as money makes money, so knowledge already acquired facilitates
the acquisition of more knowledge. It is equally evident in the case of
the method, which will now engage our attention. The progress of
science, and of knowledge generally, is frequently facilitated by
supplementing the simpler inductive methods by deductive reasoning from
knowledge already acquired. Such a combination of deduction with
induction, J. S. Mill called the «Deductive Method,» by which he really
meant the «Deductive Method of Induction.» To avoid the confusion of the
«Deductive Method» with mere deduction, which is only one part of the
whole method, it is better to describe it as the «Deductive-Inductive
Method» or the «Inductive-Deductive Method.» Mill distinguished two
principal forms of this method as applied to the study of natural
phenomena, -namely, (1) that form of it in which deduction precedes
induction, and (2) that in which induction precedes deduction. The first
of these (1) he called the «Physical Method»; the second (2) he called
the «Historical Method.»

These names are rather misleading, inasmuch as both forms of the method
are frequently employed in physics, where sometimes, say in the study of
light, mathematical (i.e., deductive) calculations precede and suggest
physical experiments (i.e., induction), and sometimes the inductive
results of observation or experiment provide the occasion or stimulus
for mathematical deductions. In any case, the differences in order of
sequence are of no great importance, and hardly deserve separate names.
What is of importance is to note the principal kinds of occasion, which
call for the use of this combined method. They are mainly three in
number: (1) When an hypothesis cannot be verified (i.e., tested)
directly, but only indirectly; (2) when it is possible to systematise a
number of already established inductions, or laws, under more
comprehensive laws or theories; (3) when, owing to the difficulties of
certain problems, or on account of the lack of sufficient and suitable
instances of the phenomena under investigation, it is considered
desirable either to confirm an inductive result by independent deductive
reasoning from the nature of the case in the light of previous
knowledge, or to confirm a deductive conclusion by independent inductive

An example of each of these types may help to make them clear. (1) When
Galileo was investigating the law of the velocity of falling bodies he
eventually formed the hypothesis that a body starting from rest falls
with a uniform acceleration, and that its velocity varies with the time
of its fall. But he could not devise any method for the direct
verification of this hypothesis. By mathematical deduction, however, he
arrived at the conclusion that a body falling according to his
hypothetical law would fall through a distance proportionate to the time
of its fall. This consequence could be tested by comparing the distances
and the time of falling bodies, which thus served as an indirect
verification of his hypothesis. (2) By inductions from numerous
astronomical observations made by Tycho Brahe and himself, Kepler
discovered the three familiar laws called by his name, namely, (a) that
the planets move in elliptic orbits which have the sun for one of their
foci; (6) that the velocity of a planet is such that the radius vector
(i.e., an imaginary line joining the moving planet to the sun) sweeps
out equal areas in equal periods of time; and (c) that the squares of
the periodic times of any two planets (that is, the times which they
take to complete their revolutions round the sun) are proportional to
the cubes of their mean distances from the sun. These three laws
appeared to be quite independent of each other. But Newton systematised
them all in the more comprehensive induction, or theory, of celestial
gravitation. He showed that they could all be deduced from the one law
that the planets tend to move towards each other with a force varying
directly with the product of their masses, and inversely with the square
of the distances between them. (3) H. Spencer, by comparing a number of
predominantly industrial States and also, of predominantly military
States, ancient and modern, inferred inductively that the former type of
State is democratic and gives rise to free institutions, whereas the
latter type is undemocratic and tends to oppression. As the sparse
evidence hardly permitted of a rigorous application of any of .the
inductive methods, Spencer tried to confirm his conclusion by deductive
reasoning from the nature of the case in the light of what is known
about the human mind. He pointed out that in a type of society, which is
predominantly industrial, the trading relations between individuals are
the predominant relations, and these train them to humour and consider
others. The result is a democratic attitude in all. In a State, which is
predominantly military, the relations which are most common among its
members are those of authority, on the one part, and of subordination on
the other. The result is the reverse of a democratic atmosphere.


In conclusion, I would like to discuss the relation of epistemology
to other branches of philosophy. Philosophy viewed in the broadest
possible terms divides into many branches: metaphysics, ethics,
aesthetics, logic, philosophy of language, philosophy of mind,
philosophy of science, and a gamut of others. Each of these disciplines
has its special subject matter: for metaphysics it is the ultimate
nature of the world; for ethics, the nature of the good life and how
people ideally ought to comport themselves in their relations with
others; and for philosophy of science, the methodology and results of
scientific activity. Each of these disciplines attempts to arrive at a
systematic understanding of the issues that arise in its particular
domain. The word systematic is important in this connection, referring,
as explained earlier, to the construction of sets of principles or
theories that are broad-ranging, consistent, and rationally defensible.
In effect, such theories can be regarded as sets of complex claims about
the various matters that are under consideration.

Epistemology stands in a close and special relationship to each of
these disciplines. Though the various divisions of philosophy differ in
their subject matter and often in the approaches taken by philosophers
to their characteristic questions, they have one feature in common: the
desire to arrive at the truth about that with which they are
concerned—say, about the fundamental ingredients of the world or about
the nature of the good life for man. If no such claims were asserted,
there would be no need for epistemology. But, once theses have been
advanced, positions staked out, and theories proposed, the
characteristic questions of epistemology inexorably follow. How can one
know that any such claim is true? What is the evidence in favour of (or
against) it? Can the claim be proven? Virtually all of the branches of
philosophy thus give rise to epistemological ponderings.

These ponderings may be described as first-order queries. They in
turn inevitably generate others that are, as it were, second-order
queries, and which are equally or more troubling. What is it to know
something? What counts as evidence for or against a particular theory?
What is meant by a proof? Or even, as the Greek Sceptics asked, is human
knowledge possible at all, or is human access to the world such that no
knowledge and no certitude about it is possible? The answers to these
second-order questions also require the construction of theories, and in
this respect epistemology is no different from the other branches of
philosophy. One can thus define or characterise epistemology as that
branch of philosophy, which is dedicated to the resolution of such
first- and second-order queries.


A preface to the logic of science, by Peter Alexander, Sheed and Ward,
London and New York, 1963.

Popper selections, edited by Dawid Miller, Princeton University press,

The critical approach to science and philosophy, edited by Mario Bunge,
The free press of Glencoe Collier- Magmillan limited, London, 1964.

Britannica encyclopaedia, 1948.

Logic without metaphysics, by Ernest Nagel, Glencoe, Ill..: Free Press,

«Epistemology, History of,», by D.W. Hamlyn. The Encyclopaedia of

Introduction to Objectivist Epistemology, expanded 2nd ed., by Ayn Rand,
New York: Penguin Group, 1990.



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