A theory isn't true until it is proven true.

Can a Theory be True?

A theory can be true or not true, all we know about a scientific theory is that it has predictive power and hasn’t been proven wrong by experiment yet.

To understand this logic we will need to cover the scientific method and explain the difference between theory in common language, scientific theory, philosophical truth, and absolute truth (with the help of Richard Feynman).

Feynman: Knowing versus Understanding.

TIP: For deeper insight into truth see how we proved “everything that can be true can be proven true” is a myth.

What is a Theory?

We may think of theory as “speculation,” but scientific theories are well-substantiated explanations based on facts and testing.

A theory can be true even if never proven, it can get some parts wrong and some parts right, or can be false even when it is long held and substantiated by experiment and fact.[1]

The only rule is, that once we prove a theory wrong via experiment, we know the theory is not true.

If the predictive power of the theory falters even once, the theory is discarded.

Proving absolute truth is much harder than proving a theory hasn’t been proved false.

Luckily truth doesn’t deepened on us to understanding or proving it, everything is either true or not independent of our understanding.

Thus we can say, “a theory can be true even if never proven”.

The video below sums up why truth is distinct from science, and points out facts such as “a theory is only as good as the experiments designed to test it”.

TIP: Another word for theory is “model.” A theory is a model that works to help us to understand any subject better. When a better theory comes a long, or when an old theory is proven false, we discard the old theory. A good scientific theory can output empirically confirmable truths, and can thus be considered true, even when aspects of the theory can’t be proven true or false with 100% certainty. In other words, a theory is a type of probable and useful truth, but it isn’t the same thing as a fact. We discuss more nuances of theories below, including how scientific theories differ from more metaphysical ones.

The Times and Troubles of the Scientific Method.

The Scientific Method

In simple terms, the Scientific Method is the process used to develop a scientific theory. One starts with a hypothesis, or group of hypotheses (which are educated “guesses” based on fact), then one designs experiments meant to disprove the predictive power of hypothesis. If any part of the theory is disproved, or the underlying hypothesis is disproved, the theory is discarded and the process repeats.

Feynman on Scientific Method. This is a pretty amazing introduction to the scientific method by Richard Feynman.

In ways, the point of science is to disprove theories, not to prove them. Instead of all instances of something working, you look only for one instance of it not working. This, by definition, implies that theories can be true without us being able to prove them, or vice versa.

The truth is the truth and it exists independent of our understanding, science only helps us to understand that which already is.

See an Introduction to the Scientific Method.

The scientific method.

What is a Scientific Theory?

The whole goal of science is to constantly question what we think we know and put theories to rigorous testing using the scientific method. A good scientific theory is a theory that has “predictive power”, has been pushed to the limits with rigorous testing, and has many facts pointing to it (typically facts rooted in math, physics, and chemistry). In the same way a philosopher questions what can’t be known, an experimental scientist questions what can be known, trying their best to break even the most long-standing and highly revered theories.

A video explaining the difference between “theory” in every language and scientific theory.

FACT: Good theories have “predictive power”. That means if a theory is good, we should be able to use it to make predictions and those predictions should be accurate. The theory that works over-and-over again has a higher likely-hood of being true. Scientific theories must work 100% of the time to earn the title “theory”.

FACT: We can also show this line of thinking (that a theory can be true despite proof) to be correct using methods such as the mathematic equation called Bayes’ Theorem, which (in simple terms) allows us to calculate the probability of truth by assigning values to the facts of a theory.

“Theory” Versus Scientific Theory?

In common language, a theory is a broad term that can mean anything from “guessing” to “conjecture”, and can be based on little or no evidence. This is not true of scientific theory.

In the field of science, a theory is a well-substantiated explanation based on a body of facts that can repeatedly be confirmed through testing, experimentation, and observation. Scientific theories are developed and verified by the scientific community and are accepted as fact (although they are constantly put to the test). If a theory stops working, even once, then it is no longer a scientific theory.[2]

Longstanding theories work in real life computations over and over again, and so may be very useful and accurate even if they can’t themselves be proven as fact.

Scientific theories aren’t infallible, but are none-the-less highly regarded scientific knowledge. They are used to make falsifiable or testable predictions and are used every day in technology and science to advance our society.

Consider the following theories:

We have a hundred years or more worth of evidence for the above theories, but some ideas remain theories because science is very particular about terminology.

If we waited to prove every theory to be a fact before believing it, we might be waiting forever. Some things, for example, things that happened in the past, can’t be proven without a time machine. Rather than focusing on testing theories, scientists can concentrate on disproving theories. If a theory is proven wrong, even just in one instance, it is no longer considered a scientific theory.

A video explaining the difference between fact, theory, law, and hypothesis.

TIP: One can have a scientific theory in regards to social science (like psychology or economics), but this is a little different than theories rooted in something like physics or biology. This is a point of contention in academics, but generally we have to make sure to understand the difference between the different arts and sciences, each requires a unique understanding of how the scientific method is applied and what can be expected from results.

Theories Are Sometimes Wrong, But Typically they Are on the Right Track

As noted above, no matter how many times a scientific theory works or how many facts point to it being true, there is always room for error. Consider the theories of the past that “the sun revolved around the earth” or that space was made of “aether”.

Sometimes traditional theories are quietly disposed of in favor of new ones; sometimes a theory changes based on new evidence. Typically we don’t go back and say we got the theory wrong, rather we get a new proof of a new, more useful, related theory and focus on that. For instance, the “aether” we thought the world was made up of is eerily close to dark matter and quantum fluctuation fields. We were wrong about aether, but we weren’t that off-base. The same can be said for “sciences” like alchemy. We used to believe that alchemy could explain the nature of matter, and could allow us to change one type of matter into another. Now we now use physics and chemistry. Again, we had some specifics wrong, but the basic idea was there.

Typically when we get something wrong, it’s because we misunderstand what the facts mean. Consider that we thought the sun revolved around the earth based on what we could observe at the time. When we became able to perceive things better by using mathematics and the telescope, astronomers changed their theory to one of the earth revolving around the sun. The church pushed back against the new theory of heliocentrism; the scientists were concerned with what they now knew and less concerned with established belief systems.

We can often accept a scientific theory as fact, but we shouldn’t confuse facts, theories, laws, and hypotheses with each other. Science uses a vast array of terminology on purpose.

A theory can be true.

When Copernicus theorized the earth revolved around the sun, he was right… his theory was off-base, but his hypothesis was right. In other words, a theory or more-so a hypothesis can be true even if we can’t prove it.

Facts, Theories, Laws, and Hypothesis

In the field of science:

  • A scientific fact is an objective and verifiable observation that can be proven undoubtedly true.
  • A scientific theory is a well-educated hypothesis based on facts and testing that explains some aspects of the universe.
  • A scientific law is a statement based on repeated experimental observations that describes some aspects of the universe
  • A scientific hypothesis is an “educated guess,” based on prior knowledge and observation.
  • The Truth is a philosophical concept meaning that something is undoubtedly a fact but does not require proof.

In everyday terms:

  • A fact may be a factoid that may or may not have evidence or truth.
  • Theory may be anything someone thinks may be true for any reason.
  • A hypothesis may be anything someone thinks may be true for any reason.
  • Law is likely to refer to legislation.
  • The truth may be a way to describe something that appears to be true regardless of whether it is true or not.

As you can see from the above, it would be a mistake to confuse scientific terms with the general meaning of the terms.

An Example of a Theory Being True: Dmitri Mendeleev’s Periodic Table

Let’s take the periodic table for an example of a theory being true.

We used to know the properties of some elements as fact (we observed them existing and measured their properties repeatedly), but we didn’t know all the elements we do today.

Around the 1869 Dmitri Mendeleev published a periodic table in which he arranged the elements he was aware of by the properties they had. This left missing elements. He theorized that these elements should exist, based on the facts he had. Further experimentation, testing, and observation proved that his theory was a fact. The missing elements were found and fit into the table neatly.

Not all theories can be proved to be facts, but knowing this, we can also know that even if we had never proved the existence of the missing elements, they would have still existed. Thus, his theory is truly independent of our ability to prove or disprove it.

FACT: We used to think the elements were earth, the wind, water, and fire, and that alchemy combined elements. Today we know the elements work a little different, and chemistry and physics have replaced alchemy. We weren’t that far off with our old theories, and we just had some of the puzzle pieces in the wrong order.

What is Truth?

In basic terms, truth is something that is not false. Facts are true; myths are not true. Truth does not require proof to be true for it to be true. It does, however, compel us to be unable to prove it false.

Philosophically, truth exists independently of our ability to prove it true. Thus, a theory can be true or untrue. In the field of science, theories can hold different degrees of truth and experiments can be done to validate or disprove any given theory without it ever being proven entirely true or false.

Often we have theories that we may never be able to demonstrate, so we are focusing on disproving them. If a theory lacks evidence that refutes it and holds up to repeated scientific testing, we tend to believe that it is true.

Absence of Evidence and Evidence of Absence

“Absence of evidence is not evidence of absence”. Something is not true because evidence to prove it untrue doesn’t exist. Likewise, something is not necessarily true because no evidence proves it incorrect.

In other words proving and disproving something with evidence and testing points us toward the truth, but a lack of understanding or a lack of evidence doesn’t imply truth or the absence of truth.

Can We Prove a Theory True?

A theory is a model of some kind that can predict observable phenomena. In general, we can disprove theories, but can’t necessarily always prove theories.[3]

We don’t have to prove something to be correct for it to be true. Truth exists independently of our understanding of a thing or our ability to prove a theory.


A theory can be true. Some theories have a lot of evidence to support them, others don’t. So each theory must be judged on it’s own merit, it would be incorrect to think that the word theory implies that something isn’t true, or vice versa implies truth.

Truth is quality that exists independent of our understanding or evidence. In science things aren’t called theories until they have met rigorous testing, even a hypothesis is an “educated guess,” based on prior knowledge and observation. Only in a loose sense of the word does theory imply “not knowing”.


  1. What is a Scientific Theory?”
  2. The Evolution of the Cell”
  3. Why can a scientific theory only be disproven and not proven?”
  4. Evidence of absence”

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