In philosophy, empiricism is a theory that
states that knowledge comes only or primarily
from sensory experience.
It is one of several views of epistemology,
the study of human knowledge, along with rationalism
and skepticism.
Empiricism emphasises the role of empirical
evidence in the formation of ideas, over the
idea of innate ideas or traditions.
However, empiricists may argue that traditions
(or customs) arise due to relations of previous
sense experiences.Empiricism in the philosophy
of science emphasises evidence, especially
as discovered in experiments.
It is a fundamental part of the scientific
method that all hypotheses and theories must
be tested against observations of the natural
world rather than resting solely on a priori
reasoning, intuition, or revelation.
Empiricism, often used by natural scientists,
says that "knowledge is based on experience"
and that "knowledge is tentative and probabilistic,
subject to continued revision and falsification".
Empirical research, including experiments
and validated measurement tools, guides the
scientific method.
== Etymology ==
The English term empirical derives from the
Ancient Greek word ἐμπειρία, empeiria
(roughly ”in test”), which is cognate
with and translates to the Latin experientia,
from which are derived the word experience
and the related experiment.
== History ==
=== 
Background ===
A central concept in science and the scientific
method is that it must be empirically based
on the evidence of the senses.
Both natural and social sciences use working
hypotheses that are testable by observation
and experiment.
The term semi-empirical is sometimes used
to describe theoretical methods that make
use of basic axioms, established scientific
laws, and previous experimental results in
order to engage in reasoned model building
and theoretical inquiry.
Philosophical empiricists hold no knowledge
to be properly inferred or deduced unless
it is derived from one's sense-based experience.
This view is commonly contrasted with rationalism,
which states that knowledge may be derived
from reason independently of the senses.
For example, John Locke held that some knowledge
(e.g. knowledge of God's existence) could
be arrived at through intuition and reasoning
alone.
Similarly Robert Boyle, a prominent advocate
of the experimental method, held that we have
innate ideas.
The main continental rationalists (Descartes,
Spinoza, and Leibniz) were also advocates
of the empirical "scientific method".
=== Early empiricism ===
Vaisheshika darsana, founded by the ancient
Indian philosopher Kanada, accepted perception
and inference as the only two reliable sources
of knowledge.
This is enumerated in his work Vaiśeṣika
Sūtra.
The earliest Western proto-empiricists were
the Empiric school of ancient Greek medical
practitioners, who rejected the three doctrines
of the Dogmatic school, preferring to rely
on the observation of "phenomena".The notion
of tabula rasa ("clean slate" or "blank tablet")
connotes a view of mind as an originally blank
or empty recorder (Locke used the words "white
paper") on which experience leaves marks.
This denies that humans have innate ideas.
The image dates back to Aristotle:
What the mind (nous) thinks must be in it
in the same sense as letters are on a tablet
(grammateion) which bears no actual writing
(grammenon); this is just what happens in
the case of the mind.
(Aristotle, On the Soul, 3.4.430a1).
Aristotle's explanation of how this was possible
was not strictly empiricist in a modern sense,
but rather based on his theory of potentiality
and actuality, and experience of sense perceptions
still requires the help of the active nous.
These notions contrasted with Platonic notions
of the human mind as an entity that pre-existed
somewhere in the heavens, before being sent
down to join a body on Earth (see Plato's
Phaedo and Apology, as well as others).
Aristotle was considered to give a more important
position to sense perception than Plato, and
commentators in the Middle Ages summarized
one of his positions as "nihil in intellectu
nisi prius fuerit in sensu" (Latin for "nothing
in the intellect without first being in the
senses").
This idea was later developed in ancient philosophy
by the Stoic school.
Stoic epistemology generally emphasized that
the mind starts blank, but acquires knowledge
as the outside world is impressed upon it.
The doxographer Aetius summarizes this view
as "When a man is born, the Stoics say, he
has the commanding part of his soul like a
sheet of paper ready for writing upon."
During the Middle Ages Aristotle's theory
of tabula rasa was developed by Islamic philosophers
starting with Al Farabi, developing into an
elaborate theory by Avicenna and demonstrated
as a thought experiment by Ibn Tufail.
For Avicenna (Ibn Sina), for example, the
tabula rasa is a pure potentiality that is
actualized through education, and knowledge
is attained through "empirical familiarity
with objects in this world from which one
abstracts universal concepts" developed through
a "syllogistic method of reasoning in which
observations lead to propositional statements
which when compounded lead to further abstract
concepts".
The intellect itself develops from a material
intellect (al-'aql al-hayulani), which is
a potentiality "that can acquire knowledge
to the active intellect (al-'aql al-fa'il),
the state of the human intellect in conjunction
with the perfect source of knowledge".
So the immaterial "active intellect", separate
from any individual person, is still essential
for understanding to occur.
In the 12th century CE the Andalusian Muslim
philosopher and novelist Abu Bakr Ibn Tufail
(known as "Abubacer" or "Ebn Tophail" in the
West) included the theory of tabula rasa as
a thought experiment in his Arabic philosophical
novel, Hayy ibn Yaqdhan in which he depicted
the development of the mind of a feral child
"from a tabula rasa to that of an adult, in
complete isolation from society" on a desert
island, through experience alone.
The Latin translation of his philosophical
novel, entitled Philosophus Autodidactus,
published by Edward Pococke the Younger in
1671, had an influence on John Locke's formulation
of tabula rasa in An Essay Concerning Human
Understanding.A similar Islamic theological
novel, Theologus Autodidactus, was written
by the Arab theologian and physician Ibn al-Nafis
in the 13th century.
It also dealt with the theme of empiricism
through the story of a feral child on a desert
island, but departed from its predecessor
by depicting the development of the protagonist's
mind through contact with society rather than
in isolation from society.During the 13th
century Thomas Aquinas adopted the Aristotelian
position that the senses are essential to
mind into scholasticism.
Bonaventure (1221–1274), one of Aquinas'
strongest intellectual opponents, offered
some of the strongest arguments in favour
of the Platonic idea of the mind.
=== Renaissance Italy ===
In the late renaissance various writers began
to question the medieval and classical understanding
of knowledge acquisition in a more fundamental
way.
In political and historical writing Niccolò
Machiavelli and his friend Francesco Guicciardini
initiated a new realistic style of writing.
Machiavelli in particular was scornful of
writers on politics who judged everything
in comparison to mental ideals and demanded
that people should study the "effectual truth"
instead.
Their contemporary, Leonardo da Vinci (1452–1519)
said, "If you find from your own experience
that something is a fact and it contradicts
what some authority has written down, then
you must abandon the authority and base your
reasoning on your own findings."The decidedly
anti-Aristotelian and anti-clerical music
theorist Vincenzo Galilei (c. 1520 – 1591),
father of Galileo and the inventor of monody,
made use of the method in successfully solving
musical problems, firstly, of tuning such
as the relationship of pitch to string tension
and mass in stringed instruments, and to volume
of air in wind instruments; and secondly to
composition, by his various suggestions to
composers in his Dialogo della musica antica
e moderna (Florence, 1581).
The Italian word he used for "experiment"
was esperienza.
It is known that he was the essential pedagogical
influence upon the young Galileo, his eldest
son (cf. Coelho, ed.
Music and Science in the Age of Galileo Galilei),
arguably one of the most influential empiricists
in history.
Vincenzo, through his tuning research, found
the underlying truth at the heart of the misunderstood
myth of 'Pythagoras' hammers' (the square
of the numbers concerned yielded those musical
intervals, not the actual numbers, as believed),
and through this and other discoveries that
demonstrated the fallibility of traditional
authorities, a radically empirical attitude
developed, passed on to Galileo, which regarded
"experience and demonstration" as the sine
qua non of valid rational enquiry.
=== British empiricism ===
British empiricism, though it was not a term
used at the time, derives from the 17th century
period of early modern philosophy and modern
science.
The term became useful in order to describe
differences perceived between two of its founders
Francis Bacon, described as empiricist, and
René Descartes, who is described as a rationalist.
Thomas Hobbes and Baruch Spinoza, in the next
generation, are often also described as an
empiricist and a rationalist respectively.
John Locke, George Berkeley, and David Hume
were the primary exponents of empiricism in
the 18th century Enlightenment, with Locke
being normally known as the founder of empiricism
as such.
In response to the early-to-mid-17th century
"continental rationalism" John Locke (1632–1704)
proposed in An Essay Concerning Human Understanding
(1689) a very influential view wherein the
only knowledge humans can have is a posteriori,
i.e., based upon experience.
Locke is famously attributed with holding
the proposition that the human mind is a tabula
rasa, a "blank tablet", in Locke's words "white
paper", on which the experiences derived from
sense impressions as a person's life proceeds
are written.
There are two sources of our ideas: sensation
and reflection.
In both cases, a distinction is made between
simple and complex ideas.
The former are unanalysable, and are broken
down into primary and secondary qualities.
Primary qualities are essential for the object
in question to be what it is.
Without specific primary qualities, an object
would not be what it is.
For example, an apple is an apple because
of the arrangement of its atomic structure.
If an apple was structured differently, it
would cease to be an apple.
Secondary qualities are the sensory information
we can perceive from its primary qualities.
For example, an apple can be perceived in
various colours, sizes, and textures but it
is still identified as an apple.
Therefore, its primary qualities dictate what
the object essentially is, while its secondary
qualities define its attributes.
Complex ideas combine simple ones, and divide
into substances, modes, and relations.
According to Locke, our knowledge of things
is a perception of ideas that are in accordance
or discordance with each other, which is very
different from the quest for certainty of
Descartes.
A generation later, the Irish Anglican bishop,
George Berkeley (1685–1753), determined
that Locke's view immediately opened a door
that would lead to eventual atheism.
In response to Locke, he put forth in his
Treatise Concerning the Principles of Human
Knowledge (1710) an important challenge to
empiricism in which things only exist either
as a result of their being perceived, or by
virtue of the fact that they are an entity
doing the perceiving.
(For Berkeley, God fills in for humans by
doing the perceiving whenever humans are not
around to do it.)
In his text Alciphron, Berkeley maintained
that any order humans may see in nature is
the language or handwriting of God.
Berkeley's approach to empiricism would later
come to be called subjective idealism.The
Scottish philosopher David Hume (1711–1776)
responded to Berkeley's criticisms of Locke,
as well as other differences between early
modern philosophers, and moved empiricism
to a new level of skepticism.
Hume argued in keeping with the empiricist
view that all knowledge derives from sense
experience, but he accepted that this has
implications not normally acceptable to philosophers.
He wrote for example, "Locke divides all arguments
into demonstrative and probable.
On this view, we must say that it is only
probable that all men must die or that the
sun will rise to-morrow, because neither of
these can be demonstrated.
But to conform our language more to common
use, we ought to divide arguments into demonstrations,
proofs, and probabilities—by ‘proofs’
meaning arguments from experience that leave
no room for doubt or opposition."
And,
"I believe the most general and most popular
explication of this matter, is to say [See
Mr. Locke, chapter of power.], that finding
from experience, that there are several new
productions in matter, such as the motions
and variations of body, and concluding that
there must somewhere be a power capable of
producing them, we arrive at last by this
reasoning at the idea of power and efficacy.
But to be convinced that this explication
is more popular than philosophical, we need
but reflect on two very obvious principles.
First, That reason alone can never give rise
to any original idea, and secondly, that reason,
as distinguished from experience, can never
make us conclude, that a cause or productive
quality is absolutely requisite to every beginning
of existence.
Both these considerations have been sufficiently
explained: and therefore shall not at present
be any farther insisted on."
Hume divided all of human knowledge into two
categories: relations of ideas and matters
of fact (see also Kant's analytic-synthetic
distinction).
Mathematical and logical propositions (e.g.
"that the square of the hypotenuse is equal
to the sum of the squares of the two sides")
are examples of the first, while propositions
involving some contingent observation of the
world (e.g. "the sun rises in the East") are
examples of the second.
All of people's "ideas", in turn, are derived
from their "impressions".
For Hume, an "impression" corresponds roughly
with what we call a sensation.
To remember or to imagine such impressions
is to have an "idea".
Ideas are therefore the faint copies of sensations.
Hume maintained that no knowledge, even the
most basic beliefs about the natural world,
can be conclusively established by reason.
Rather, he maintained, our beliefs are more
a result of accumulated habits, developed
in response to accumulated sense experiences.
Among his many arguments Hume also added another
important slant to the debate about scientific
method—that of the problem of induction.
Hume argued that it requires inductive reasoning
to arrive at the premises for the principle
of inductive reasoning, and therefore the
justification for inductive reasoning is a
circular argument.
Among Hume's conclusions regarding the problem
of induction is that there is no certainty
that the future will resemble the past.
Thus, as a simple instance posed by Hume,
we cannot know with certainty by inductive
reasoning that the sun will continue to rise
in the East, but instead come to expect it
to do so because it has repeatedly done so
in the past.Hume concluded that such things
as belief in an external world and belief
in the existence of the self were not rationally
justifiable.
According to Hume these beliefs were to be
accepted nonetheless because of their profound
basis in instinct and custom.
Hume's lasting legacy, however, was the doubt
that his skeptical arguments cast on the legitimacy
of inductive reasoning, allowing many skeptics
who followed to cast similar doubt.
=== Phenomenalism ===
Most of Hume's followers have disagreed with
his conclusion that belief in an external
world is rationally unjustifiable, contending
that Hume's own principles implicitly contained
the rational justification for such a belief,
that is, beyond being content to let the issue
rest on human instinct, custom and habit.
According to an extreme empiricist theory
known as phenomenalism, anticipated by the
arguments of both Hume and George Berkeley,
a physical object is a kind of construction
out of our experiences.
Phenomenalism is the view that physical objects,
properties, events (whatever is physical)
are reducible to mental objects, properties,
events.
Ultimately, only mental objects, properties,
events, exist—hence the closely related
term subjective idealism.
By the phenomenalistic line of thinking, to
have a visual experience of a real physical
thing is to have an experience of a certain
kind of group of experiences.
This type of set of experiences possesses
a constancy and coherence that is lacking
in the set of experiences of which hallucinations,
for example, are a part.
As John Stuart Mill put it in the mid-19th
century, matter is the "permanent possibility
of sensation".
Mill's empiricism went a significant step
beyond Hume in still another respect: in maintaining
that induction is necessary for all meaningful
knowledge including mathematics.
As summarized by D.W.
Hamlin:
[Mill] claimed that mathematical truths were
merely very highly confirmed generalizations
from experience; mathematical inference, generally
conceived as deductive [and a priori] in nature,
Mill set down as founded on induction.
Thus, in Mill's philosophy there was no real
place for knowledge based on relations of
ideas.
In his view logical and mathematical necessity
is psychological; we are merely unable to
conceive any other possibilities than those
that logical and mathematical propositions
assert.
This is perhaps the most extreme version of
empiricism known, but it has not found many
defenders.
Mill's empiricism thus held that knowledge
of any kind is not from direct experience
but an inductive inference from direct experience.
The problems other philosophers have had with
Mill's position center around the following
issues: Firstly, Mill's formulation encounters
difficulty when it describes what direct experience
is by differentiating only between actual
and possible sensations.
This misses some key discussion concerning
conditions under which such "groups of permanent
possibilities of sensation" might exist in
the first place.
Berkeley put God in that gap; the phenomenalists,
including Mill, essentially left the question
unanswered.
In the end, lacking an acknowledgement of
an aspect of "reality" that goes beyond mere
"possibilities of sensation", such a position
leads to a version of subjective idealism.
Questions of how floor beams continue to support
a floor while unobserved, how trees continue
to grow while unobserved and untouched by
human hands, etc., remain unanswered, and
perhaps unanswerable in these terms.
Secondly, Mill's formulation leaves open the
unsettling possibility that the "gap-filling
entities are purely possibilities and not
actualities at all".
Thirdly, Mill's position, by calling mathematics
merely another species of inductive inference,
misapprehends mathematics.
It fails to fully consider the structure and
method of mathematical science, the products
of which are arrived at through an internally
consistent deductive set of procedures which
do not, either today or at the time Mill wrote,
fall under the agreed meaning of induction.The
phenomenalist phase of post-Humean empiricism
ended by the 1940s, for by that time it had
become obvious that statements about physical
things could not be translated into statements
about actual and possible sense data.
If a physical object statement is to be translatable
into a sense-data statement, the former must
be at least deducible from the latter.
But it came to be realized that there is no
finite set of statements about actual and
possible sense-data from which we can deduce
even a single physical-object statement.
The translating or paraphrasing statement
must be couched in terms of normal observers
in normal conditions of observation.
There is, however, no finite set of statements
that are couched in purely sensory terms and
can express the satisfaction of the condition
of the presence of a normal observer.
According to phenomenalism, to say that a
normal observer is present is to make the
hypothetical statement that were a doctor
to inspect the observer, the observer would
appear to the doctor to be normal.
But, of course, the doctor himself must be
a normal observer.
If we are to specify this doctor's normality
in sensory terms, we must make reference to
a second doctor who, when inspecting the sense
organs of the first doctor, would himself
have to have the sense data a normal observer
has when inspecting the sense organs of a
subject who is a normal observer.
And if we are to specify in sensory terms
that the second doctor is a normal observer,
we must refer to a third doctor, and so on
(also see the third man).
=== Logical empiricism ===
Logical empiricism (also logical positivism
or neopositivism) was an early 20th-century
attempt to synthesize the essential ideas
of British empiricism (e.g. a strong emphasis
on sensory experience as the basis for knowledge)
with certain insights from mathematical logic
that had been developed by Gottlob Frege and
Ludwig Wittgenstein.
Some of the key figures in this movement were
Otto Neurath, Moritz Schlick and the rest
of the Vienna Circle, along with A.J.
Ayer, Rudolf Carnap and Hans Reichenbach.
The neopositivists subscribed to a notion
of philosophy as the conceptual clarification
of the methods, insights and discoveries of
the sciences.
They saw in the logical symbolism elaborated
by Frege (1848–1925) and Bertrand Russell
(1872–1970) a powerful instrument that could
rationally reconstruct all scientific discourse
into an ideal, logically perfect, language
that would be free of the ambiguities and
deformations of natural language.
This gave rise to what they saw as metaphysical
pseudoproblems and other conceptual confusions.
By combining Frege's thesis that all mathematical
truths are logical with the early Wittgenstein's
idea that all logical truths are mere linguistic
tautologies, they arrived at a twofold classification
of all propositions: the analytic (a priori)
and the synthetic (a posteriori).
On this basis, they formulated a strong principle
of demarcation between sentences that have
sense and those that do not: the so-called
verification principle.
Any sentence that is not purely logical, or
is unverifiable is devoid of meaning.
As a result, most metaphysical, ethical, aesthetic
and other traditional philosophical problems
came to be considered pseudoproblems.In the
extreme empiricism of the neopositivists—at
least before the 1930s—any genuinely synthetic
assertion must be reducible to an ultimate
assertion (or set of ultimate assertions)
that expresses direct observations or perceptions.
In later years, Carnap and Neurath abandoned
this sort of phenomenalism in favor of a rational
reconstruction of knowledge into the language
of an objective spatio-temporal physics.
That is, instead of translating sentences
about physical objects into sense-data, such
sentences were to be translated into so-called
protocol sentences, for example, "X at location
Y and at time T observes such and such."
The central theses of logical positivism (verificationism,
the analytic–synthetic distinction, reductionism,
etc.) came under sharp attack after World
War II by thinkers such as Nelson Goodman,
W.V.
Quine, Hilary Putnam, Karl Popper, and Richard
Rorty.
By the late 1960s, it had become evident to
most philosophers that the movement had pretty
much run its course, though its influence
is still significant among contemporary analytic
philosophers such as Michael Dummett and other
anti-realists.
=== 
Pragmatism ===
In the late 19th and early 20th century several
forms of pragmatic philosophy arose.
The ideas of pragmatism, in its various forms,
developed mainly from discussions between
Charles Sanders Peirce and William James when
both men were at Harvard in the 1870s.
James popularized the term "pragmatism", giving
Peirce full credit for its patrimony, but
Peirce later demurred from the tangents that
the movement was taking, and redubbed what
he regarded as the original idea with the
name of "pragmaticism".
Along with its pragmatic theory of truth,
this perspective integrates the basic insights
of empirical (experience-based) and rational
(concept-based) thinking.
Charles Peirce (1839–1914) was highly influential
in laying the groundwork for today's empirical
scientific method.
Although Peirce severely criticized many elements
of Descartes' peculiar brand of rationalism,
he did not reject rationalism outright.
Indeed, he concurred with the main ideas of
rationalism, most importantly the idea that
rational concepts can be meaningful and the
idea that rational concepts necessarily go
beyond the data given by empirical observation.
In later years he even emphasized the concept-driven
side of the then ongoing debate between strict
empiricism and strict rationalism, in part
to counterbalance the excesses to which some
of his cohorts had taken pragmatism under
the "data-driven" strict-empiricist view.
Among Peirce's major contributions was to
place inductive reasoning and deductive reasoning
in a complementary rather than competitive
mode, the latter of which had been the primary
trend among the educated since David Hume
wrote a century before.
To this, Peirce added the concept of abductive
reasoning.
The combined three forms of reasoning serve
as a primary conceptual foundation for the
empirically based scientific method today.
Peirce's approach "presupposes that (1) the
objects of knowledge are real things, (2)
the characters (properties) of real things
do not depend on our perceptions of them,
and (3) everyone who has sufficient experience
of real things will agree on the truth about
them.
According to Peirce's doctrine of fallibilism,
the conclusions of science are always tentative.
The rationality of the scientific method does
not depend on the certainty of its conclusions,
but on its self-corrective character: by continued
application of the method science can detect
and correct its own mistakes, and thus eventually
lead to the discovery of truth".
In his Harvard "Lectures on Pragmatism" (1903),
Peirce enumerated what he called the "three
cotary propositions of pragmatism" (L: cos,
cotis whetstone), saying that they "put the
edge on the maxim of pragmatism".
First among these he listed the peripatetic-thomist
observation mentioned above, but he further
observed that this link between sensory perception
and intellectual conception is a two-way street.
That is, it can be taken to say that whatever
we find in the intellect is also incipiently
in the senses.
Hence, if theories are theory-laden then so
are the senses, and perception itself can
be seen as a species of abductive inference,
its difference being that it is beyond control
and hence beyond critique—in a word, incorrigible.
This in no way conflicts with the fallibility
and revisability of scientific concepts, since
it is only the immediate percept in its unique
individuality or "thisness"—what the Scholastics
called its haecceity—that stands beyond
control and correction.
Scientific concepts, on the other hand, are
general in nature, and transient sensations
do in another sense find correction within
them.
This notion of perception as abduction has
received periodic revivals in artificial intelligence
and cognitive science research, most recently
for instance with the work of Irvin Rock on
indirect perception.Around the beginning of
the 20th century, William James (1842–1910)
coined the term "radical empiricism" to describe
an offshoot of his form of pragmatism, which
he argued could be dealt with separately from
his pragmatism—though in fact the two concepts
are intertwined in James's published lectures.
James maintained that the empirically observed
"directly apprehended universe needs ... no
extraneous trans-empirical connective support",
by which he meant to rule out the perception
that there can be any value added by seeking
supernatural explanations for natural phenomena.
James' "radical empiricism" is thus not radical
in the context of the term "empiricism", but
is instead fairly consistent with the modern
use of the term "empirical".
His method of argument in arriving at this
view, however, still readily encounters debate
within philosophy even today.
John Dewey (1859–1952) modified James' pragmatism
to form a theory known as instrumentalism.
The role of sense experience in Dewey's theory
is crucial, in that he saw experience as unified
totality of things through which everything
else is interrelated.
Dewey's basic thought, in accordance with
empiricism was that reality is determined
by past experience.
Therefore, humans adapt their past experiences
of things to perform experiments upon and
test the pragmatic values of such experience.
The value of such experience is measured experientially
and scientifically, and the results of such
tests generate ideas that serve as instruments
for future experimentation, in physical sciences
as in ethics.
Thus, ideas in Dewey's system retain their
empiricist flavour in that they are only known
a posteriori.
== See also ==
Abstract empiricism
Concept empiricism
Empirical formula
Empirical idealism
Empirical realism
Empirical relationship
Empirical research
Feminist empiricism
Ground truth
History of scientific method
Inquiry
Kantian empiricism
Materialism and Empiriocriticism
Natural philosophy
Naturalism
Objectivity
Psychological nativism
Quasi-empirical method
Sensualism
Sextus Empiricus
Transcendental empiricism
"Two Dogmas of Empiricism"
== Endnotes
