I. Definition

The English word knowledge can mean familiarity, capability (know-how), theoretical knowledge (knowledge-that), or recorded knowledge. It can be explicit, as in a statement, implicit, as in your knowing how to walk, or a bit of both, like your knowledge of language.

Knowledge is one of the biggest ideas in religion, philosophy, and science, close as it is to the ideas ‘truth’ and ‘reality.’  Plato famously defined knowledge as “justified true belief.”  Philosophers agree that this definition is incomplete but it’s a good place to start: an idea which is true (which has been justified).

In religion or spirituality, knowledge may refer to knowledge of spirit, god(s), transcendental reality, consciousness, or nature.  In some religions, this kind of knowledge comes from believing the words of scripture or clergy, while in others it comes through direct personal experience, which is known as ‘mysticism.’ All major religions include both theoretical and mystical traditions.  Theoretical religious knowledge includes things like the ten commandments and the story of Genesis.  Mystical knowledge is the result of meditation or other mind altering practices, such as in Christian Gnosticism, Jewish Kabbalah, and Islamic Sufi-ism.  All major religions have also valued scholarship in general, at least in some of their sects, or in some time periods, although some have tried to limit scholars to their own religious beliefs (see section two)

Philosophers also seem split between these two kinds of knowledge—theoretical and direct.  Western philosophy, from which science was born, has always obsessed about theoretical knowledge, such as measurement, language, and logic.  In the East, philosophy has been intimately involved with mystical spiritual practices.  But many western philosophers have also discussed direct knowledge, mystical and otherwise, while Eastern philosophy has also produced a vast body of literature concerning logic and theoretical knowledge.  How to know anything for sure has always been the most fundamental problem in philosophy, since it is a necessary foundation for all other philosophy and science (see section three).

Science is, basically, the quest for theoretical knowledge, regarded in the West as the highest and surest form of knowledge, because we have a method for testing its validity (within limits).  Because only measurable things can be tested in this way, science has become committed to the idea that ‘reality’ means ‘physical, observable, and objective.’ Quantum physics, anthropology, and cognitive science have somewhat thrown these assumptions into question, but not in ways which necessarily compromise the scientific method; the twentieth century has raised new questions about the nature of reality and knowledge, but the scientific method remains the best method we know for deriving knowledge.


II. History of Knowledge

Depending on how narrowly or broadly you define knowledge, it’s history could go back to the beginning of life, or merely to ancient Greece.  All living things embody some know-how, in the broadest sense, and some aspects of life on Earth—DNA, immune systems, and the gut—seem to possess knowledge, in some sense, about the body, mind, environment, and other living things, such as bacteria. Apes and some other animals can develop knowledge in a more human sense, such as when chimpanzees learn from their parents how to use rocks and sticks to acquire food.

Human knowledge in pre-history is demonstrated by artifacts such as tools, buildings, and art, which goes back nearly 50,000 years. But the first evidence of a true consciousness of knowledge is probably the invention of writing, at the same time as the first city-states, in the Middle-East, 5,000 years ago.  The 2,000-years-plus of history and culture following that invention, but before ancient Greece, produced vast amounts of writing, but without much care, if any, for distinguishing knowledge from belief, imagination, legend, mythology, or rumor.  They certainly recorded a lot which they might have thought of as knowledge, such as astronomy, history, and medicine, but before ancient Greece few people made any effort to determine the truth of their knowledge.

A far as we know, the ancient Greeks were the first to theorize about knowledge, as ‘truth justified by evidence,’ although philosophers in the East were also doing so at about the same time.  Even then, while some Greek philosophers regarded knowledge as pertaining only to justified facts about physical reality, many also still believed in innate or direct knowledge of spirit, nature, or morality.  Those who expressed skepticism in traditional religious belief, could, in some times and places, be condemned as heretics and sentenced to death. Socrates and Epicurus were both accused of heresy for promoting skepticism, even though they both claimed to believe in the gods (unlike Socrates, Epicurus got away with it).  Greek philosophers such as Aristotle, Euclid, Pythagoras, and others, laid the foundations of math and logic for modern science, while most of them claimed to believe in spiritual knowledge as well.

During the time of ancient Greece and Rome, the East was also in the process of developing philosophical knowledge, especially in the vast literatures of Hindu and Buddhist philosophy in India, Tibet, and China.  Although they emphasized spiritual knowledge discovered through contemplation, they also developed systems of logic and philosophies of truth as sophisticated as those of the west—much of which remains untranslated.

Meanwhile, the Dark Ages of Catholic dominance came and severely hampered western science for 1,000 years, while scientific knowledge continued to develop, off and on, in the more free-thinking Islamic, Indian, and Chinese civilizations.  The European Renaissance is said to have been sparked, in part, by the reception in Europe of scientific and philosophical ideas taken from the Islamic Ottoman Empire during the Crusades. Many western sciences today—such as chemistry, astronomy, and algebra—are littered with Arabic words inherited at that time.

During the 17th and 18th centuries, rationalism and empiricism transformed European attitudes about knowledge into those we think of as the scientific world-view today. Sir Francis Bacon explicitly defined the scientific method, and many scientists, such as Isaac Newton, used that method to derive more reliable and comprehensive theoretical knowledge of nature than ever before.  Ironically, this was the beginning of a process which would culminate in many, perhaps most, modern scientists regarding mystical knowledge as nothing but delusion and superstition, although some of the greatest scientists, such as Newton, were themselves mystics.

During the early 20th century, another great revolution in knowledge took place, which has yet to be fully assimilated by many humans–the discoveries that what is true depends on how something is observed, in what frame of reference, and expressed in what language.  Although some might argue that cultural relativity doesn’t apply to knowledge about the physical world, new developments in physics itself have proven that the properties of the physical world are partially determined by how you look at it.

Some philosophers in the 19th century, such as Nietzsche had already suspected that that there might be no such thing as objective truth, i.e. no true knowledge, and this view was already becoming widespread even before physics, psychology, anthropology, linguistics, and other fields began to justify it in the 20th century.  Which brings us to the greatest controversy about knowledge—is there any, and if so, what can we know for sure?


III. Controversies about Knowledge

Is there such a thing as knowledge, and what can we be sure about?

You’ve heard some version of the saying, “true wisdom is knowing that you know nothing.”  Variations on this saying have been attributed to Confucius, Socrates, and other great wise persons.  Of course, in one sense, the phrase is just praising humility, and perhaps you’ve never thought about its more radical implication—that nobody can ever truly know anything.  This idea has always haunted philosophy and science, whose purposes are the discovery of truth (i.e. knowledge).

The Greek skeptics were among the earliest philosophies which insisted that all truths should be questioned.  Buddhism and Taoism, which appeared in China around the same time, voiced a related idea—that reality was inherently beyond words, so no verbal statement can represent knowledge.  Most linguists, psychologists, and anthropologists agree with this, while a lot of mathematicians and scientists seem to believe that it is theoretically possible, using enough words, or the right math, to represent genuine knowledge.

However, 20th century math and science have proven that even if knowledge is not impossible, is must always be incomplete.  The mathematician Kurt Gödel proved that there must always be true statements which cannot be proven.  Quantum physics proved that the properties of sub-atomic particles can only be determined within certain limits.  And linguists showed that language and logic are much less literal than they seem, calling the objectivity of much scientific language into question.

Ideas like these have always frustrated people who believe absolute knowledge is possible, whether religious or scientific.  But a committed belief in objective knowledge can only be a faith.  So even scientists and philosophers with dogmatic ideas recognize that discovering knowledge depends on some degree of skepticism.

Several philosophers have tried to settle the question of what can be known for sure.  As you’ve probably heard, Descartes settled on “I think therefore I am,” however, Buddhists claim that if you meditate further you will realize that “I” and “am” can also be doubted and the only thing remaining is consciousness, without an “I.” Edmund Husserl tried to establish a method for making only true statements, called the phenomenological reduction; basically, he taught that the only things anyone can know for sure are that they are experiencing such-and-such at a given moment.  This became one of the foundational ideas of existentialism, which considers moment-to-moment experience as the most fundamental reality, rather than any transcendental realm.

Late twentieth century philosophy was hit with digesting the realization that all expressed knowledge must be interpreted relative to culture and language, prompting many to deny again the possibility of absolute knowledge.  Most educated thinkers today seem to agree with this idea in principle but many ignore it and act as if math, science, or mysticism gives access to real knowledge.  This is not so much a form of ignorance as pragmatism; even if there is no perfect knowledge, science, math, philosophy, and mysticism still give us ways to learn a lot about reality.


IV. Quotes about Knowledge

Quotation #1:

“Philosophy … is a science, and as such has no articles of faith; accordingly, in it nothing can be assumed as existing except what is either positively given empirically, or demonstrated through indubitable conclusions.” ― Arthur Schopenhauer, Parerga and Paralipomena

Here, Schopenhauer summarizes the scientific position on knowledge.  He implies by “positively” the philosophy of positivism, which would mean that only measurable physical phenomena count as observable knowledge.  By indubitable, he means ‘proven with sound logic.’  However, note that these are only criteria for what can be “assumed as existing.”  Schopenhauer does not rule out the consideration and exploration of less sure knowledge; in fact, he was one of the first modern western philosophers with an interest in Eastern philosophy.

Quotation #2:

“I have been and still am a seeker, but I have ceased to question stars and books; I have begun to listen to the teaching my blood whispers to me.”
― Hermann Hesse, Demian. Die Geschichte von Emil Sinclairs Jugend

This poetic quotation can represent the alternative to theoretical knowledge—direct (mystical) knowledge of reality.  Hesse, wrote much fiction about mysticism, such as his most loved novel Siddhartha.  Here he describes an experience familiar to many well-read people, growing tired of words and explicit knowledge, and becoming attracted to the wordless knowledge (if that’s what it is) available through sensitive inward observing.

Quotation #3:

“To light a candle is to cast a shadow…” ― Ursula K. Le Guin, A Wizard of Earthsea

Ursula K. Leguin, an author of children’s books, adult fiction, poetry, and philosophy, makes an important and unusual point about knowledge—that knowing one thing always obscures something else.


V. Types of Knowledge

There are many ways of classifying knowledge, philosophical and otherwise.  Here is a list covering the most important distinctions:

Knowledge-that or descriptive, propositional, or explicit knowledge: these various terms all describe the same thing—knowledge which can be expressed in statements made of words and other symbols.  This has always been the main kind of knowledge of interest to philosophers.  This kind of knowledge makes a claim about something, rather than simply being a piece of evidence or a perception.  Therefore, it can be evaluated as true or false, unlike implicit knowledge.

Knowledge-how or implicit, tacit, or procedural knowledge: these terms are not exactly the same, but close enough for our purposes.  This the ability to do something, such as ride a bike, play a musical instrument, or speak a language.  In other words, this knowledge is not easily describable in words, if at all, and although one can do any of these things well or badly, implicit knowledge can’t be true or false, just effective or ineffective.  Implicit knowledge is believed to live in the unconscious mind, which has only been a subject of study since about the 1950s.

A priori knowledge: “A priori” means ‘before’ and includes statements which can be known to be true before making any empirical observations, such as for example, X=X.  Given the laws of deductive inference, it is possible to discover a priori knowledge, which is considered indubitable by most philosophers.

A posteriori knowledge: “A posteriori” means ‘after’ and includes statements of truth which can inferred by generalizing from observations, or inductive inference. This kind of knowledge is not considered as reliable as “a priori” knowledge because it could always be violated by later observations; ‘a posteriori knowledge’ is typically only true within limits.

Phenomenological knowledge: This is not a common phrase, but it best describes a most important type of knowledge—the direct knowledge of experience.  Although it’s not a common term, it is considered a foundation of modern philosophy, since the only thing other than ‘a priori’ knowledge which cannot be doubted is that you seem to be having such-and-such an experience.


VI. Knowledge versus Wisdom

Most people intuitively feel that knowledge is different from wisdom, but the difference is difficult to define.  Aristotle defined wisdom as practical knowledge of what is good or right, developed by applying insight to one’s experiences over time.  This definition implies that wisdom can be implicit or explicit—it can mean knowing-how or knowing-that—and it’s about knowing the best thing to do, not what is true.  All cultures seem to respect and admire wisdom, perhaps because it depends on experience and insight, whereas any fool can get some knowledge, just by reading a book.


VII. Knowledge in Pop Culture

Example #1: The Matrix: ‘I know kung fu’

In this scene from the ever-philosophical Matrix film trilogy, Keanu Reeves’ character, Neo, has just had a thorough knowledge of kung fu uploaded into his brain.  In reality, this might never be possible because it involves procedural knowledge hard-wired into the brain through long conditioning.  But the scene discusses knowledge in other ways: Morpheus (Lawrence Fishburne) prods Neo to question his apparent reality which is a computer simulation, and to ‘free his mind’ by choosing to ‘know’ what he can do, which is really a form of faith.  In this case, since physical reality is an illusion, and Neo can do whatever he believes in, the Wachowski brothers have turned traditional philosophical ideas on their heads!

Example #2: Dr. Strange:

In this scene, Benedict Cumberbatch, as Dr. Strange, first meets and argues with Tilda Swinton, as “The Ancient One.”  The doctor, a world-leading brain surgeon, ridicules the idea of faith, and then expresses his faith that only the material world is real. The Ancient One, representing mysticism, responds by giving him direct knowledge of the spiritual world.  Of course, the doctor immediately raises the possibility that it was a drug-induced hallucination, alluding to the scientific position that such experiences do not provide reliable knowledge, as we could be dreaming or otherwise deluded.


Which of the following is thought by philosophers the most reliable source of knowledge?





What do Buddhist philosophers believe cannot be doubted?





Statements in the Bible would be what kind of knowledge (if they’re true)?





Knowing how to stand-up is what kind of knowledge?





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