
Observation
[https://www.dictionary.com/] is the active acquisition of
information
Information is processed, organised and structured data
Data (; ) are individual facts
A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated to c ...

from a
primary source
In the study of history
History (from Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populatio ...

. In living beings, observation employs the
sense
A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology), stimuli. (For example, in the human body, the brain receives signals from the senses ...

s. In
science
Science () is a systematic enterprise that builds and organizes knowledge
Knowledge is a familiarity or awareness, of someone or something, such as facts
A fact is something that is truth, true. The usual test for a statement of ...

, observation can also involve the
perception
Perception (from the Latin
Latin (, or , ) is a classical language
A classical language is a language
A language is a structured system of communication
Communication (from Latin ''communicare'', meaning "to share" o ...

and recording of
data
Data (; ) are individual facts
A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated to correspond to experience. Standard reference works are often used ...
via the use of
scientific instrument
A scientific instrument is a device or tool used for scientific purposes, including the study of both natural phenomena and theoretical research.
History
Historically, the definition of a scientific instrument has varied, based on usage, laws, and ...
s. The term may also refer to any data collected during the scientific activity. Observations can be
qualitative, that is, only the absence or presence of a property is noted, or
quantitative if a numerical value is attached to the observed
phenomenon
A phenomenon (; plural phenomena) is an observable
In physics
Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...
by
counting
Counting is the process of determining the number of Element (mathematics), elements of a finite set of objects, i.e., determining the size (mathematics), size of a set. The traditional way of counting consists of continually increasing a (mental ...
or
measuring
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the context and discipline. In natural science
Natu ...

.
Science
The
scientific method
The scientific method is an empirical
Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence ...

requires observations of
natural phenomena
Nature, in the broadest sense, is the natural, physical, material world or universe
The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...
to formulate and test
hypotheses
A hypothesis (plural hypotheses) is a proposed explanation
An explanation is a set of statements usually constructed to describe a set of facts which clarifies the causes, context
Context may refer to:
* Context (language use), the rel ...
.
It consists of the following steps:
# Ask a
question
A question is an utterance which typically functions as a request for information, which is expected to be provided in the form of an answer. Questions can thus be understood as a kind of illocutionary act The concept of illocutionary acts was i ...

about a natural
phenomenon
A phenomenon (; plural phenomena) is an observable
In physics
Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...
# Make observations of the phenomenon
# Formulate a
hypothesis
A hypothesis (plural hypotheses) is a proposed explanation
An explanation is a set of statements usually constructed to describe a set of facts which clarifies the causes, context
Context may refer to:
* Context (language use), the rel ...
that tentatively answers the question
#
Predict logical, observable
consequences of the hypothesis that have not yet been investigated
# Test the hypothesis' predictions by an
experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome oc ...

,
observational study
In fields such as epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and risk factor, determinants of health and disease conditions in defined populations.
It is a cornerstone of public hea ...
,
field study
Field research, field studies, or fieldwork is the collection of raw data outside a laboratory
A laboratory (, ; colloquially lab) is a facility that provides controlled conditions in which science, scientific or technological researc ...

, or
simulation
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the simulat ...

# Draw a
conclusion from
data
Data (; ) are individual facts
A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated to correspond to experience. Standard reference works are often used ...

gathered in the experiment, or revise the hypothesis or form a new one and
repeat the process
# Write a
descriptive method of observation and the
result
A result (also called upshot) is the final consequence of a sequence
In mathematics
Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes a ...

s or conclusions reached
# Have peers with experience researching the same phenomenon
evaluate
Evaluation is a
systematic determination of a subject's merit, worth and significance, using criteria governed by a set of Standardization, standards. It can assist an organization, program, design, project or any other intervention or initiative ...
the results
Observations play a role in the second and fifth steps of the scientific method. However, the need for
reproducibility
Reproducibility, also known as replicability and repeatability, is a major principle underpinning the scientific method
The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterized the develop ...
requires that observations by different observers can be comparable. Human
sense
A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology), stimuli. (For example, in the human body, the brain receives signals from the senses ...

impressions are
subjective
Subjective may refer to:
* Subjectivity, a subject's personal perspective, feelings, beliefs, desires or discovery, as opposed to those made from an independent, objective, point of view
** Subjective experience, the subjective quality of consciou ...
and
qualitative, making them difficult to record or compare. The use of
measurement
Measurement is the quantification (science), quantification of variable and attribute (research), attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependen ...

was developed to allow recording and comparison of observations made at different times and places, by different people. The measurement consists of using observation to compare the phenomenon being observed to a
standard unit. The standard unit can be an artifact, process, or definition which can be duplicated or shared by all observers. In measurement, the number of standard units which is equal to the observation is counted. Measurement reduces an observation to a number that can be recorded, and two observations which result in the same number are equal within the
resolution
Resolution(s) may refer to:
Common meanings
* Resolution (debate), the statement which is debated in policy debate
* Resolution (law), a written motion adopted by a deliberative body
* New Year's resolution, a commitment that an individual make ...

of the process.
Human senses are limited and subject to errors in perception, such as
optical illusion
Within visual perception
Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twil ...

s.
Scientific instrument
A scientific instrument is a device or tool used for scientific purposes, including the study of both natural phenomena and theoretical research.
History
Historically, the definition of a scientific instrument has varied, based on usage, laws, and ...
s were developed to aid human abilities of observation, such as
weighing scale
A scale or balance is a device to measure weight or mass. These are also known as mass scales, weight scales, mass balances, and weight balances.
The traditional scale consists of two plates or bowls suspended at equal distances from a Lever ...

s,
clock
A clock or a timepiece is a device used to measure and indicate time
Time is the continued sequence of existence and event (philosophy), events that occurs in an apparently irreversible process, irreversible succession from the past ...

s,
telescope
A telescope is an optical instrument
An optical instrument (or "optic" for short) is a device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine their characteristic properties. Common ...

s,
microscope
A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the naked eye
Naked eye, also called bare ...

s,
thermometer
(mercury-in-glass thermometer) for measurement of room temperature.
A thermometer is a device that temperature measurement, measures temperature or a temperature gradient
A temperature gradient is a physical quantity that describes in which dir ...

s,
camera
A camera is an optical
Optics is the branch of physics
Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and t ...

s, and
tape recorder
An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction
Sound recording and reproduction is an electrical
Electricity is the set of physical ...
s, and also translate into perceptible form events that are unobservable by the senses, such as
indicator dyes,
voltmeter
A voltmeter is an instrument used for measuring electric potential
The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the amount of work
Work may refer to:
* ...

s,
spectrometer
A spectrometer () is a scientific instrument used to separate and measure Spectrum, spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon ...

s,
infrared camera
A thermographic camera (also called an infrared camera or thermal imaging camera, thermal camera or thermal imager) is a device that creates an image using infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation ...
s,
oscilloscope
An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope
A digital storage oscilloscope (DSO) is an oscillosco ...

s,
interferometer
. The two light rays with a common source combine at the half-silvered mirror to reach the detector. They may either interfere constructively (strengthening in intensity) if their light waves arrive in phase, or interfere destructively (weakening i ...

s,
geiger counter
A Geiger counter (also known as a Geiger–Müller counter) is an electronic instrument used for detecting and measuring ionizing radiation
Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles o ...

s, and
radio receiver
In radio, radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an anten ...

s.
One problem encountered throughout scientific fields is that the observation may affect the process being observed, resulting in a different outcome than if the process was unobserved. This is called the ''
observer effect
"Observer Effect" is the eleventh episode of the Star Trek: Enterprise (season 4), fourth season of the American science fiction television series ''Star Trek: Enterprise'' and the eighty-eighth overall. It was first aired on January 21, 2005, on ...
''. For example, it is not normally possible to check the air pressure in an automobile tire without letting out some of the air, thereby changing the pressure. However, in most fields of science, it is possible to reduce the effects of observation to insignificance by using better instruments.
Considered as a physical process itself, all forms of observation (human or instrumental) involve
and are thus thermodynamically
irreversible processes
In science, a thermodynamic processes, process that is not Reversible process (thermodynamics), reversible is called irreversible. This concept arises frequently in thermodynamics.
In thermodynamics, a change in the thermodynamic state of a syste ...
, increasing
entropy
Entropy is a scientific concept as well as a measurable physical property that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamic ...

.
Paradoxes
In some specific fields of science, the results of observation differ depending on factors that are not important in everyday observation. These are usually illustrated with "
paradox
A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically u ...

es" in which an event appears different when observed from two different points of view, seeming to violate "common sense".
* Relativity: In
relativistic physics
In physics, relativistic mechanics refers to mechanics compatible with special relativity (SR) and general relativity (GR). It provides a non-quantum mechanics, quantum mechanical description of a system of particles, or of a fluid, in cases where ...
which deals with velocities close to the
speed of light
The speed of light in vacuum
A vacuum is a space
Space is the boundless three-dimensional
Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called paramet ...
, it is found that different observers may observe different values for the length, time rates, mass, and many other properties of an object, depending on the observer's velocity relative to the object. For example, in the
twin paradox
In physics, the twin paradox is a thought experiment in special relativity involving identical twins, one of whom makes a journey into space in a high-speed rocket and returns home to find that the twin who remained on Earth has aged more. Thi ...

one twin goes on a trip near the speed of light and comes home younger than the twin who stayed at home. This is not a paradox: time passes at a slower rate when measured from a frame moving concerning the object. In relativistic physics, an observation must always be qualified by specifying the state of motion of the observer, its
reference frame
In physics, a frame of reference (or reference frame) consists of an abstract coordinate system
In geometry
Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, wi ...

.
* Quantum mechanics: In
quantum mechanics
Quantum mechanics is a fundamental theory
A theory is a reason, rational type of abstraction, abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with ...
, which deals with the behavior of very small objects, it is not possible to
observe a system without changing the system, and the "observer" must be considered part of the
system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole.
A system, surrounded and influenced by its environment, is described by its boundaries, structure and purp ...

being observed. In isolation, quantum objects are represented by a
wave function
A wave function in quantum physics
Quantum mechanics is a fundamental theory
A theory is a rational
Rationality is the quality or state of being rational – that is, being based on or agreeable to reason
Reason is the capacity ...

which often exists in a
superposition or mixture of different
states
State may refer to:
Arts, entertainment, and media Literature
* ''State Magazine'', a monthly magazine published by the U.S. Department of State
* The State (newspaper), ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, Un ...
. However, when an observation is made to determine the actual location or state of the object, it always finds the object in a single state, not a "mixture". The interaction of the observation process appears to "
collapse
Collapse or its variants may refer to:
Concepts
* Collapse (structural)
* Collapse (topology), a mathematical concept
* Collapsing manifold
* Collapse, the action of collapsing or telescoping objects
* Ecosystem collapse
An ecosystem
...
" the wave function into a single state. So any interaction between an isolated wave function and the external world that results in this wave function collapse is called an ''observation'' or ''measurement'', whether or not it is part of a deliberate observation process.
Biases
The human senses do not function like a video
camcorder
A camcorder is an electronic device originally combining a video camera
A video camera is a camera
A camera is an optical
Optics is the branch of physics
Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗ ...

, impartially recording all observations.
Human perception occurs by a complex, unconscious process of
abstraction
Abstraction in its main sense is a conceptual process where general rules
Rule or ruling may refer to:
Human activity
* The exercise of political
Politics (from , ) is the set of activities that are associated with Decision-making, mak ...

, in which certain details of the incoming sense data are noticed and remembered, and the rest is forgotten. What is kept and what is thrown away depends on an internal model or representation of the world, called by psychologists a ''
schema
The word schema comes from the Greek word ('), which means ''shape'', or more generally, ''plan''. The plural is ('). In English, both ''schemas'' and ''schemata'' are used as plural forms.
Schema may refer to:
Science and technology
* SCHEMA ...
'', that is built up over our entire lives. The data is fitted into this schema. Later when events are remembered, memory gaps may even be filled by "plausible" data the mind makes up to fit the model; this is called ''
reconstructive memory
Reconstructive memory is a theory of memory recall, in which the act of remembering is influenced by various other cognitive processes including perception, imagination, semantic memory
Semantic memory is one of the two types of explicit memo ...
''. How much attention the various perceived data are given depends on an internal value system, which judges how important it is to the individual. Thus two people can view the same event and come away with entirely different perceptions of it, even disagreeing about simple facts. This is why
eyewitness testimony
Eyewitness testimony is the account a bystander or victim gives in the courtroom, describing what that person observed that occurred during the specific incident under investigation. Ideally this recollection of events is detailed; however, this is ...
is notoriously unreliable.
Several of the more important ways observations can be affected by human psychology are given below.
Confirmation bias
Human observations are biased toward confirming the observer's conscious and unconscious expectations and view of the world; we "''see what we expect to see''".
In psychology, this is called
confirmation bias
Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms or supports one's prior belief
A belief is an attitude
Attitude may refer to:
Philosophy and psychology
* Attitude (psycholo ...
.
Since the object of scientific research is the
discovery
Discovery may refer to:
* Discovery (observation)
Discovery is the act of detecting something new, or something previously unrecognized as meaningful. With reference to sciences and academic disciplines
An academic discipline or academic fi ...
of new phenomena, this bias can and has caused new discoveries to be overlooked; one example is the discovery of
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation
In physics
Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Moti ...

s. It can also result in erroneous scientific support for widely held cultural myths, on the other hand, as in the
scientific racism
Scientific racism, sometimes termed biological racism, is the pseudoscientific
Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method. Pseu ...
that supported ideas of racial superiority in the early 20th century.
Correct scientific technique emphasizes careful recording of observations, separating experimental observations from the conclusions drawn from them, and techniques such as
blind
Blind may refer to:
* The state of Visual impairment, blindness, being unable to see
* A window blind, a covering for a window
Blind may also refer to:
Arts, entertainment, and media Films
* Blind (2007 film), ''Blind'' (2007 film), a 2007 Dut ...
or
double blind experiments, to minimize observational bias.
Processing bias
Modern scientific instruments can extensively process "observations" before they are presented to the human senses, and particularly with computerized instruments, there is sometimes a question as to where in the data processing chain "observing" ends and "drawing conclusions" begins. This has recently become an issue with
digitally enhanced images published as experimental data in
papers
Paper is a thin, flat material produced by the compression of fibres.
Paper(s) or The Paper may also refer to:
Publishing and academia
* Newspaper, a periodical publication
* Paper (magazine), ''Paper'' (magazine), an American monthly fashion and ...
in
scientific journal
In academic publishing
Academic publishing is the subfield of publishing which distributes academic research and scholarship. Most academic work is published in academic journal articles, books or thesis' form. The part of academic written ...
s. The images are enhanced to bring out features that the researcher wants to emphasize, but this also has the effect of supporting the researcher's conclusions. This is a form of bias that is difficult to quantify. Some
scientific journal
In academic publishing
Academic publishing is the subfield of publishing which distributes academic research and scholarship. Most academic work is published in academic journal articles, books or thesis' form. The part of academic written ...
s have begun to set detailed standards for what types of
image processing
Digital image processing is the use of a digital computer
A computer is a machine
A machine is a man-made device that uses power to apply forces and control movement to perform an action. Machines can be driven by animals and people
...
are allowed in research results. Computerized instruments often keep a copy of the "raw data" from sensors before processing, which is the ultimate defense against processing bias, and similarly, scientific standards require preservation of the original unenhanced "raw" versions of images used as research data.
Philosophy
Observation in
philosophical
Philosophy (from , ) is the study of general and fundamental questions, such as those about existence
Existence is the ability of an entity to interact with physical or mental reality
Reality is the sum or aggregate of all that is real o ...

terms is the process of filtering
information
Information is processed, organised and structured data
Data (; ) are individual facts
A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated to c ...

through the thought process. Input is received via
hearing
Hearing, or auditory perception, is the ability to perceive sounds
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, ...
,
sight
Visual perception is the ability to interpret the surrounding environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biol ...
,
smell,
taste
The gustatory system or sense of taste is the sensory system
The sensory nervous system is a part of the nervous system
In biology
Biology is the natural science that studies life and living organisms, including their anatomy, ph ...

, or
touch
The somatosensory system is a part of the sensory nervous system
The sensory nervous system is a part of the nervous system
In biology, the classical doctrine of the nervous system determines that it is a Complex system, highly comple ...
and then analyzed through either rational or irrational thought.
For example, let us suppose that an observer ''sees'' a parent beat their child and consequently may observe that such an action is either good or bad. Deductions about what behaviors are good or bad may be based on preferences about building relationships, or the study of the consequences resulting from the observed behavior. Over time, impressions stored in the consciousness about many, together with the resulting relationships and consequences, permit the individual to build a construct about the moral implications of behavior.
See also
*
Deixis
In linguistics
Linguistics is the scientific study of language
A language is a structured system of communication
Communication (from Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic ...

*
Introspection
Introspection is the examination of one's own conscious
, an English Paracelsian
Paracelsianism (also Paracelsism; German: ') was an early modern History of medicine, medical movement based on the theories and therapies of Paracelsus.
It de ...
*
List of cognitive biases
Cognitive bias
A cognitive bias is a systematic pattern of deviation from norm (philosophy), norm or rationality in judgment. Individuals create their own "subjective reality" from their perception of the input. An individual's construction of rea ...
*
Metaphysics of presence
The concept of the metaphysics of presence is an important consideration in deconstruction
Deconstruction is an approach to understanding the relationship between text and meaning. It was originated by the philosopher Jacques Derrida (1930–2 ...
*
Naturalistic observation
Naturalistic observation, sometimes referred to as fieldwork
Field research, field studies, or fieldwork is the empirical research, collection of raw data outside a laboratory, library, or workplace setting. The approaches and methods used in ...
*
Observation unit
*
Observational astronomy
Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data (information), data via the use of scienti ...
*
Observational error
Observational error (or measurement error) is the difference between a measured value of a quantity and its true value.Dodge, Y. (2003) ''The Oxford Dictionary of Statistical Terms'', OUP. In statistics
Statistics is the discipline that co ...
*
Observational learning
Observational learning is learning that occurs through observing the behavior of others. It is a form of social learning which takes various forms, based on various processes. In humans, this form of learning seems to not need reinforcement to o ...
*
Observational study
In fields such as epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and risk factor, determinants of health and disease conditions in defined populations.
It is a cornerstone of public hea ...
*
Observable quantity
*
Observations and Measurements
*
Observatory
An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been cons ...

*
Observer effect
"Observer Effect" is the eleventh episode of the Star Trek: Enterprise (season 4), fourth season of the American science fiction television series ''Star Trek: Enterprise'' and the eighty-eighth overall. It was first aired on January 21, 2005, on ...
*
Present
The present (or here and now) is the time that is associated with the events perception, perceived directly and in the first time, not as a recollection (perceived more than once) or a speculation (predicted, hypothesis, uncertain). It is a per ...

*
Self
The self is an individual person as the object of its own reflective consciousness
Consciousness, at its simplest, is or of internal and external existence. Despite millennia of analyses, definitions, explanations and debates by philosoph ...

*
Theory ladenness
*
Uncertainty principle
In quantum mechanics
Quantum mechanics is a fundamental Scientific theory, theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quant ...

*
UnobservableAn unobservable (also called impalpable) is an entity whose existence, nature, properties, qualities or relations are not directly observable by humans. In philosophy of science
Philosophy of science is a branch of philosophy concerned with th ...
References
{{philosophy of science
Aptitude
Cognition
Epistemology of science
Experiments
Knowledge
Metaphysics of mind
Ontology
Perception
Philosophy of mind
Philosophy of science
Scientific method
A scientific method is a sequence or collection of processes that are considered characteristic of scientific investigation and the acquisition of new scientific knowledge based upon physical evidence
Evidence, broadly construed, is anything p ...
Sources of knowledge