implications of science. The central questions of this study concern what qualifies as science,

the reliability of scientific theories, and the ultimate purpose of science. This discipline

overlaps with metaphysics, ontology, and epistemology, for example, when it explores the relationship

between science and truth. There is no consensus among philosophers about

many of the central problems concerned with the philosophy of science, including whether

science can reveal the truth about unobservable things and whether scientific reasoning can

be justified at all. In addition to these general questions about science as a whole,

philosophers of science consider problems that apply to particular sciences (such as

biology or physics). Some philosophers of science also use contemporary results in science

to reach conclusions about philosophy itself. While philosophical thought pertaining to

science dates back at least to the time of Aristotle, philosophy of science emerged as

a distinct discipline only in the 20th century in the wake of the logical positivism movement,

which aimed to formulate criteria for ensuring all philosophical statements' meaningfulness

and objectively assessing them. Thomas Kuhn's 1962 book The Structure of Scientific Revolutions

was also formative, challenging the view of scientific progress as steady, cumulative

acquisition of knowledge based on a fixed method of systematic experimentation and instead

arguing that any progress is relative to a "paradigm," the set of questions, concepts,

and practices that define a scientific discipline in a particular historical period. Karl Popper

and Charles Sanders Peirce moved on from positivism to establish a modern set of standards for

scientific methodology. Subsequently, the coherentist approach to

science, in which a theory is validated if it makes sense of observations as part of

a coherent whole, became prominent due to W. V. Quine and others. Some thinkers such

as Stephen Jay Gould seek to ground science in axiomatic assumptions, such as the uniformity

of nature. A vocal minority of philosophers, and Paul Feyerabend (1924–1994) in particular,

argue that there is no such thing as the "scientific method", so all approaches to science should

be allowed, including explicitly supernatural ones. Another approach to thinking about science

involves studying how knowledge is created from a sociological perspective, an approach

represented by scholars like David Bloor and Barry Barnes. Finally, a tradition in continental

philosophy approaches science from the perspective of a rigorous analysis of human experience.

Philosophies of the particular sciences range from questions about the nature of time raised

by Einstein's general relativity, to the implications of economics for public policy. A central

theme is whether one scientific discipline can be reduced to the terms of another. That

is, can chemistry be reduced to physics, or can sociology be reduced to individual psychology?

The general questions of philosophy of science also arise with greater specificity in some

particular sciences. For instance, the question of the validity of scientific reasoning is

seen in a different guise in the foundations of statistics. The question of what counts

as science and what should be excluded arises as a life-or-death matter in the philosophy

of medicine. Additionally, the philosophies of biology, of psychology, and of the social

sciences explore whether the scientific studies of human nature can achieve objectivity or

are inevitably shaped by values and by social relations.

== Introduction ==

=== Defining science ===

Distinguishing between science and non-science is referred to as the demarcation problem.

For example, should psychoanalysis be considered science? How about so-called creation science,

the inflationary multiverse hypothesis, or macroeconomics? Karl Popper called this the

central question in the philosophy of science. However, no unified account of the problem

has won acceptance among philosophers, and some regard the problem as unsolvable or uninteresting.

Martin Gardner has argued for the use of a Potter Stewart standard ("I know it when I

see it") for recognizing pseudoscience.Early attempts by the logical positivists grounded

science in observation while non-science was non-observational and hence meaningless. Popper

argued that the central property of science is falsifiability. That is, every genuinely

scientific claim is capable of being proven false, at least in principle.An area of study

or speculation that masquerades as science in an attempt to claim a legitimacy that it

would not otherwise be able to achieve is referred to as pseudoscience, fringe science,

or junk science. Physicist Richard Feynman coined the term "cargo cult science" for cases

in which researchers believe they are doing science because their activities have the

outward appearance of it but actually lack the "kind of utter honesty" that allows their

results to be rigorously evaluated.

=== Scientific explanation ===

A closely related question is what counts as a good scientific explanation. In addition

to providing predictions about future events, society often takes scientific theories to

provide explanations for events that occur regularly or have already occurred. Philosophers

have investigated the criteria by which a scientific theory can be said to have successfully

explained a phenomenon, as well as what it means to say a scientific theory has explanatory

power. One early and influential theory of scientific

explanation is the deductive-nomological model. It says that a successful scientific explanation

must deduce the occurrence of the phenomena in question from a scientific law. This view

has been subjected to substantial criticism, resulting in several widely acknowledged counterexamples

to the theory. It is especially challenging to characterize what is meant by an explanation

when the thing to be explained cannot be deduced from any law because it is a matter of chance,

or otherwise cannot be perfectly predicted from what is known. Wesley Salmon developed

a model in which a good scientific explanation must be statistically relevant to the outcome

to be explained. Others have argued that the key to a good explanation is unifying disparate

phenomena or providing a causal mechanism.

=== Justifying science ===

Although it is often taken for granted, it is not at all clear how one can infer the

validity of a general statement from a number of specific instances or infer the truth of

a theory from a series of successful tests. For example, a chicken observes that each

morning the farmer comes and gives it food, for hundreds of days in a row. The chicken

may therefore use inductive reasoning to infer that the farmer will bring food every morning.

However, one morning, the farmer comes and kills the chicken. How is scientific reasoning

more trustworthy than the chicken's reasoning? One approach is to acknowledge that induction

cannot achieve certainty, but observing more instances of a general statement can at least

make the general statement more probable. So the chicken would be right to conclude

from all those mornings that it is likely the farmer will come with food again the next

morning, even if it cannot be certain. However, there remain difficult questions about the

process of interpreting any given evidence into a probability that the general statement

is true. One way out of these particular difficulties is to declare that all beliefs about scientific

theories are subjective, or personal, and correct reasoning is merely about how evidence

should change one's subjective beliefs over time.Some argue that what scientists do is

not inductive reasoning at all but rather abductive reasoning, or inference to the best

explanation. In this account, science is not about generalizing specific instances but

rather about hypothesizing explanations for what is observed. As discussed in the previous

section, it is not always clear what is meant by the "best explanation." Ockham's razor,

which counsels choosing the simplest available explanation, thus plays an important role

in some versions of this approach. To return to the example of the chicken, would it be

simpler to suppose that the farmer cares about it and will continue taking care of it indefinitely

or that the farmer is fattening it up for slaughter? Philosophers have tried to make

this heuristic principle more precise in terms of theoretical parsimony or other measures.

Yet, although various measures of simplicity have been brought forward as potential candidates,

it is generally accepted that there is no such thing as a theory-independent measure

of simplicity. In other words, there appear to be as many different measures of simplicity

as there are theories themselves, and the task of choosing between measures of simplicity

appears to be every bit as problematic as the job of choosing between theories. Nicholas

Maxwell has argued for some decades that unity rather than simplicity is the key non-empirical

factor in influencing choice of theory in science, persistent preference for unified

theories in effect committing science to the acceptance of a metaphysical thesis concerning

unity in nature. In order to improve this problematic thesis, it needs to be represented

in the form of a hierarchy of theses, each thesis becoming more insubstantial as one

goes up the hierarchy.

=== Observation inseparable from theory ===

When making observations, scientists look through telescopes, study images on electronic

screens, record meter readings, and so on. Generally, on a basic level, they can agree

on what they see, e.g., the thermometer shows 37.9 degrees C. But, if these scientists have

different ideas about the theories that have been developed to explain these basic observations,

they may disagree about what they are observing. For example, before Albert Einstein's general

theory of relativity, observers would have likely interpreted the image at right as five

different objects in space. In light of that theory, however, astronomers will tell you

that there are actually only two objects, one in the center and four different images

of a second object around the sides. Alternatively, if other scientists suspect that something

is wrong with the telescope and only one object is actually being observed, they are operating

under yet another theory. Observations that cannot be separated from theoretical interpretation

are said to be theory-laden.All observation involves both perception and cognition. That

is, one does not make an observation passively, but rather is actively engaged in distinguishing

the phenomenon being observed from surrounding sensory data. Therefore, observations are

affected by one's underlying understanding of the way in which the world functions, and

that understanding may influence what is perceived, noticed, or deemed worthy of consideration.

In this sense, it can be argued that all observation is theory-laden.

=== The purpose of science ===

Should science aim to determine ultimate truth, or are there questions that science cannot

answer? Scientific realists claim that science aims at truth and that one ought to regard

scientific theories as true, approximately true, or likely true. Conversely, scientific

anti-realists argue that science does not aim (or at least does not succeed) at truth,

especially truth about unobservables like electrons or other universes. Instrumentalists

argue that scientific theories should only be evaluated on whether they are useful. In

their view, whether theories are true or not is beside the point, because the purpose of

science is to make predictions and enable effective technology.

Realists often point to the success of recent scientific theories as evidence for the truth

(or near truth) of current theories. Antirealists point to either the many false theories in

the history of science, epistemic morals, the success of false modeling assumptions,

or widely termed postmodern criticisms of objectivity as evidence against scientific

realism. Antirealists attempt to explain the success of scientific theories without reference

to truth. Some antirealists claim that scientific theories aim at being accurate only about

observable objects and argue that their success is primarily judged by that criterion.

=== Values and science === Values intersect with science in different

ways. There are epistemic values that mainly guide the scientific research. The scientific

enterprise is embedded in particular culture and values through individual practitioners.

Values emerge from science, both as product and process and can be distributed among several

cultures in the society. If it is unclear what counts as science, how

the process of confirming theories works, and what the purpose of science is, there

is considerable scope for values and other social influences to shape science. Indeed,

values can play a role ranging from determining which research gets funded to influencing

which theories achieve scientific consensus. For example, in the 19th century, cultural

values held by scientists about race shaped research on evolution, and values concerning

social class influenced debates on phrenology (considered scientific at the time). Feminist

philosophers of science, sociologists of science, and others explore how social values affect

science.

== History ==

=== Pre-modern ===

The origins of philosophy of science trace back to Plato and Aristotle who distinguished