Descriptive knowledge, also declarative knowledge or propositional
knowledge, is the type of knowledge that is, by its very nature,
expressed in declarative sentences or indicative propositions. This
distinguishes descriptive knowledge from what is commonly known as
"know-how", or procedural knowledge (the knowledge of how, and
especially how best, to perform some task), and "knowing of", or
knowledge by acquaintance (the knowledge of something's existence).
The difference between knowledge and beliefs is as follows: A belief
is an internal thought or memory which exists in one's mind. Most
people accept that for a belief to be knowledge it must be, at least,
true and justified. The
Gettier problem in philosophy is the question
of whether there are any other requirements before a belief can be
accepted as knowledge.
The article epistemology discusses the opinion of philosophers on how
one can tell which beliefs constitute actual knowledge.
1 Acquiring knowledge
2 Types of knowledge
Knowledge in various disciplines
Knowledge in science and engineering
Knowledge in history
4 Situated knowledge
6 Non-scientific methods
7 Practical limits for obtaining knowledge
8 See also
Knowledge acquisition (philosophy)
People have used many methods to try to gain knowledge.
By reason and logic (perhaps in cooperation with others, using logical
By mathematical proof.
By the scientific method.
By the trial and error method.
By applying an algorithm.
By learning from experience.
By intuition (getting them from the subconscious).
By an argument from authority, which could be from religious,
literary, political, philosophical or scientific authorities.
By listening to the testimony of witnesses.
By observing the world in its "natural state"; seeing how the world
operates without performing any experiments.
By acquiring knowledge that is embedded in one's language, culture, or
By dialogical enquiry (conversation). See Gadamer, Bohm, Habermas,
Freire, on dialogue, learning and knowledge acquisition/negotiation:
By enlightenment following a period of meditation. (For example, the
Buddhist enlightenment known as bodhi)
By divine illumination, prayer or revelation from a divine agency.
By the Word of
Knowledge – specific knowledge about a person that
precedes a miracle healing, well-documented among Charismatic
Christians especially since the rise of social media.
By direct perception (examples: Gibson's theory of vision, Sufi theory
Types of knowledge
Knowledge can be classified upon a priori knowledge, which is obtained
without needing to observe the world, and a posteriori or empirical
knowledge, which is only obtained after observing the world or
interacting with it in some way.
Often knowledge is gained by combining or extending other knowledge in
Isaac Newton famously wrote: "If I have seen further...
it is by standing on the shoulders of giants".
Inferential knowledge is based on reasoning from facts or from other
inferential knowledge such as a theory. Such knowledge may or may not
be verifiable by observation or testing. The distinction between
factual knowledge and inferential knowledge has been explored by the
discipline of general semantics.
Knowledge in various disciplines
There are many different disciplines that generate beliefs that can be
regarded as knowledge. They include science (which generates
scientific theories), law (which generates verdicts), history (which
generates historical narratives), and mathematics (which generates
Knowledge in science and engineering
Scientists attempt to gain knowledge through the scientific method. In
this method, scientists start by finding a phenomenon of interest,
which generates questions.
Scientist then pick a question of interest,
and based on previous knowledge, develop a hypothesis. The scientists
then design a controlled experiment which will allow them to test the
hypothesis against the real world. They then make predictions about
the outcome of the test, based on the hypothesis.
At this point, the scientists carry out the experiment and compare
their predictions with their observations. Assuming that there were no
flaws in the experiment, if the observations match the predictions,
this is evidence in favour of the hypothesis. If they do not match,
then the hypothesis has been falsified.
A hypothesis that has been shown to accurately and reliably predict
and characterize some physical phenomenon, and has been sufficiently
tested, may become a scientific theory. Scientific theories are widely
regarded as knowledge, and they are always subject to further revision
or review should new data come to light.
To use scientific theories, they must be applied to the specific
situation in hand. For example, a civil engineer might use the theory
of statics (a branch of physics) to determine whether a bridge will
hold up. This is one case where new knowledge is generated from
scientific knowledge by specializing it to an individual instance.
The nature of human reasoning dictates that even a sound piece of
scientific work might be regarded as incorrect by the scientific
community at large. This is exemplified by Dan Shechtman's discovery
in solid states for which he was criticised for some time.
Knowledge in history
The scientific method is essentially the application of the inductive
approach to investigation. This approach is entirely appropriate for
exploration of the causal world of nature (physics, chemistry, etc.)
but not valid for the teleological social sciences, which includes
history. There are no constants in human relations,
only unmeasurable and inconstant subjective valuations.[citation
needed] Electrons always behave the same way under the same
conditions, but humans do not—different people seem
to react differently and the same person seems to or might react
differently at different moments in time. Thus, it appears that only
spurious inferences can be drawn from repeated observations of human
behavior. It might be observed that most humans
prefer wealth to poverty or life to death, but it might be invalid to
infer any universal law of human behavior from this.
Historians often generate different interpretations of the same event,
even when reading the same primary sources, and these interpretations
are always subject to revision by other historians. This is because,
as a social scientist, the historian must constantly make subjective
judgements of relevance in trying to interpret historical
Situated knowledge is knowledge specific to a particular situation.
Imagine two very similar breeds of mushroom, which grow on either side
of a mountain, one nutritious, one poisonous. Relying on knowledge
from one side of an ecological boundary, after crossing to the other,
may lead to starving rather than eating perfectly healthy food near at
hand, or to poisoning oneself by mistake.
Some methods of generating knowledge, such as trial and error, or
learning from experience, tend to create highly situational knowledge.
One of the main benefits of the scientific method is that the theories
it generates are much less situational than knowledge gained by other
Situational knowledge is often embedded in language, culture, or
traditions. Critics of cultural imperialism argue that the rise of a
global monoculture causes a loss of local knowledge.
What constitutes knowledge, certainty and truth are controversial
issues. These issues are debated by philosophers, social scientists,
Ludwig Wittgenstein wrote "On Certainty" – aphorisms
on these concepts – exploring relationships between knowledge and
certainty. A thread of his concern has become an entire field, the
philosophy of action.
A number of problems exist, that arise when defining knowledge or
truth, including issues with objectivity, adequacy and limits to
justification. Beliefs are also very problematic not least because
they are either true or false, and therefore cannot be adequately
described by conventional logic. An action likewise can be taken or
not, but there is the troubling idea of an "event" is, an action taken
by nobody, or nobody whom one can blame.
Several groups, most notably the postmodernists and social
constructivists, hold that science does not actually tell us about the
physical world in which they live. They hold that the world cannot be
understood by science, but rather by religious revelations, mystical
experience, or literary deconstructionism.
Practical limits for obtaining knowledge
What we hold to be knowledge is often derived by a combination of
reason from either traditional, authoritative, or scientific sources.
Many times such knowledge is not verifiable; sometimes the process of
testing is prohibitively dangerous or expensive. For instance, some
physics theories about the nature of the universe, such as
string-theory, require the construction of testing equipment currently
beyond our technology. Since such theories are in principle subject to
verification or refutation, they are scientific; since they are not
proven experimentally, they are not considered certain knowledge.
Rather, in such cases we have certain knowledge only of the theory,
but not of what the theory describes.
"Of the three ways in which men think that they acquire knowledge of
things—authority, reasoning, and experience—only the last is
effective and able to bring peace to the intellect." (Roger Bacon,
English alchemist, astrologer, philosopher and a major progenitor of
Semiotic information theory
^ Shah, Idries. The Way of the Sufi.
The Nobel Prize in Chemistry 2011 - Press Release
Augustine of Hippo
A. J. Ayer
G. E. Moore
P. F. Strawson
Willard Van Orman Quine
Internalism and externalism
Theory of forms
A priori knowledge
Problem of induction
Problem of other minds
Outline of epistemology
Faith and rationality
Philosophy of perception
Philosophy of science