Knowledge: What It Is, How We Get It, and Why It Is Hard to Define

Knowledge is understanding that you can trust and use. It is more than a fact you have heard. A true fact only counts as knowledge when you have good reason to believe it.

That small difference has kept thinkers busy for more than 2,000 years. Most people use the word every day without a clear definition, so this article explains it in simple terms.

Knowledge, Information, and Wisdom

People often mix these words up, but they are not the same.

Information is raw material, such as a number, a date, or a headline. Knowledge appears when you understand that information and can use it. A list of train times is information. Knowing how to plan a trip with it is knowledge.

Many writers also add wisdom, which is good judgment about how and when to use what you know. This idea is often shown as a ladder: data, then information, then knowledge, then wisdom. It is a useful teaching tool, but it is not a scientific law.

Three Main Types of Knowledge

Philosophers have found it helpful to split knowledge into kinds.

Knowing that. This is knowing facts. Paris is the capital of France. Water boils at 100°C at sea level. Philosophers call this propositional knowledge.

Knowing how. This is skill. You can ride a bike, cook a meal, or play a piano piece. The philosopher Gilbert Ryle wrote about the difference between knowing that and knowing how in his 1949 book The Concept of Mind.

Knowing by experience. This means being familiar with something directly. You know the taste of coffee because you have tasted it. Bertrand Russell wrote about this idea, which he called knowledge by acquaintance, in the early 1910s.

Hidden Knowledge You Cannot Easily Explain

Some of what you know is hard to put into words. Think of recognizing a friend’s face in a crowd. You can do it, but you cannot list every detail that tells you it is them.

The scientist and philosopher Michael Polanyi called this tacit knowledge. In his 1966 book The Tacit Dimension, he wrote that we can know more than we can tell.

Businesses care about this idea too. In 1995, Ikujiro Nonaka and Hirotaka Takeuchi published The Knowledge-Creating Company. They argued that firms succeed by turning personal, hidden know-how into shared knowledge that teams can use.

How People Gain Knowledge

Philosophers usually name a few main sources:

• Perception. We learn by seeing, hearing, touching, tasting, and smelling.
• Memory. We keep what we learned before.
• Reason. We work out new ideas by thinking. Math is a clear example.
• Testimony. We learn from other people, books, teachers, and experts. Most of what any person knows comes this way. You have probably never measured the distance to the Moon, yet you know it is far away.
• Introspection. We know our own thoughts and feelings by looking inward.

Thinkers have long argued about which source matters most. Rationalists, such as René Descartes, gave reason the leading role. Empiricists, such as John Locke and David Hume, said experience comes first. Many modern thinkers say we need both.

The Old Definition and Its Problem

Around 369 BC, Plato discussed an idea in his dialogue Theaetetus that knowledge might be true belief with an account or reason behind it. Later writers shortened this to “justified true belief.” For a long time, many people treated it as the standard answer.

It has three parts. You must believe the claim. The claim must be true. You must have good reasons for believing it.

In 1963, the philosopher Edmund Gettier published a very short paper, about three pages long, called “Is Justified True Belief Knowledge?” He gave examples where a person has all three parts but still seems not to know. Here is a simple example of the kind of case he meant. It is made up for this article.

You look at a clock that shows 3:00. You believe it is 3:00. It really is 3:00. But the clock stopped exactly 12 hours ago, and you were just lucky. Your belief is true and seems justified, yet most people would say you did not truly know the time.

Philosophers have suggested many fixes since then. None has won full agreement. This is why the question “What is knowledge?” is still open.

Why Knowledge Matters

Knowledge helps people make choices, solve problems, and avoid harm. It also grows when people share it. A farmer’s tip, a doctor’s training, or a scientist’s study can help thousands of others.

Writers have long linked knowledge with power. The line “knowledge itself is power” is often tied to Francis Bacon, who used a Latin version of it in a 1597 work.

But knowledge has limits. Scientists often change their views when new evidence appears. This is not a failure. It is how science works. Good knowers hold their beliefs firmly enough to act on them, and loosely enough to change them when better evidence appears.

How to Build Reliable Knowledge

You do not need to study philosophy to know better. A few habits help:

• Ask where a claim comes from.
• Prefer sources that show their evidence.
• Check important facts in more than one independent place.
• Notice when you are only guessing.
• Practice skills, not only reading about them.
• Be willing to say, “I was wrong.”

The Short Answer

Knowledge is true understanding backed by good reasons. It comes in several kinds, including facts, skills, and personal experience. It grows through our senses, memory, thinking, and the words of others.

Philosophers still argue about its exact definition. For daily life, a simple rule works well: believe what you can support, and keep learning.