How certain are proven facts?

This is the second part of the Question Beyond Science exploring how certain we can be about what we think we know.  Yesterday’s post discussed certainty and religious belief.  This post asks whether science can provide us with absolute certainty.  Again, your feedback is warmly welcomed.

How the Scientific Method Works

The scientific method is in many ways a highly disciplined application of the kind of reasoning processes humans use all the time.

First, we experience something – we see the sun come up in the morning, for instance, and set every evening.  In a scientific study, this is what is called “data.”

Then we ask what it means, we try to explain it.  How it is, for instance, that the sun comes up every morning and sets every evening?  In science the explanation is the “theory.”

But science adds several qualifications to these steps.  The first isreplication of the data.  Scientists agree that data must be subject to being checked by other scientists.  So scientists study only objects and events that other scientists can also observe if they choose.  Whatever a scientist studies, from the stars to how people behave, the basic requirement is that other scientists can also observe and analyze it.

This is to rule out errors or fraud or even hallucinations or dreams that are mistaken for something objectively real.

The second qualification of science is in relation to theory.  Science neither accepts nor denies the existence of a supernatural world.  It does, however, look for explanations solely within the operations of the natural world.  So even if a scientist believes in God, it would not be an acceptable scientific theory to hypothesize, for instance, that the sun is under the control of a god who takes the sun away at night and brings it back every morning.

It is because science insists on data which is observable and theories which are rooted in the laws of the natural universe, that its theories can betested.

How Theory becomes Fact

A scientific theory is first developed as an explanation for something we observe.  It is then tested by examining its predictions.  The more predictions made by a theory which are correct, the stronger a theory becomes.  Each correct prediction contributes to its proof.

For tens of thousands of years, human beings looked at the data and concluded, quite reasonably, that the world was flat.  Very few people questioned what seemed to be obvious to almost anybody who had ever walked on it.  But about 500 years ago, Copernicus suggested not only that the world was shaped like a huge ball but that it was twirling around in space and at the same time whirling around the sun.  This was a whole new explanation which at first sounded preposterous.

How did we all become convinced not only that it wasn’t preposterous but was actually fact, was, in other words, true?  We became convinced because the theory predicted and explained so many other things that it began to make sense.

This new theory explained how it was that the sun seemed to set at night and come back again on the other side of the sky in the morning.  It explained the changing positions of the stars.  It explained why the seasons regularly changed from winter to summer and back again.  It explained how ships sailed around the world and got back home without ever turning around.  It explained so many things that people now say it’s not “just a theory,” but a “proven fact.”

By a similar process, Newton’s theory of gravity, Mendel’s laws of heredity, and Darwin’s theory of evolution have become “fact.”

But scientific facts, no matter how much proof backs them up, never become absolutely certain.  They may be accepted by most people for a very long time under most conditions, but scientific facts are never beyond question.


How Can a Fact that is Proved be Disproved?

Facts are disproved when the theory that explains the fact is no longer accepted.  The “fact” that the world was flat was disproved when the theory that earth was round was accepted.  The “fact” that the sun went around the world was disproved when the theory that the earth went around the sun explained things better and so was accepted by scientists and by most people.

Newton’s theory of gravity that said the universe worked like a gigantic clock is no longer accepted as fact since scientists have shown that the force of gravity isn’t strong enough to hold the world together.  The “facts” that parallel lines never meet, that a mile is always the same length, and a minute lasts just as long no matter where you are have been disproved by Einstein’s theories of relativity.

Many of these disproven facts still work quite well in our small world where we still walk on what seems to be a flat world, where the sun still comes up and goes down each day, where a mile is always 5280 feet long, and a minute always 60 seconds.

But they are not absolute facts because time and space a relative. So they aren’t certain no matter what.  No matter what the “fact,” there is always the possibility that another theory will convince us that what we thought was indisputable is not certain after all.

So although science has taught us a lot about the universe, science always deals in various levels of uncertainty.  Some levels of certainty are very high.  But it is not absolute.

What do you think?

Are there some things about which you think you can be absolutely certain?  Why or why not?

Is your certainty about scientific fact and religious belief different?

Copyright © T. Herman Sissons, Ph.D.


About Terry Sissons

Terry Sissons is the author of The Big Bang to Now: All of Time in Six Chunks, and this blog is a dialogue about the universe and what’s happened in the last 13 billions years.
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2 Responses to How certain are proven facts?

  1. Henk Meevis says:

    Hello Terry,
    Yes there are ome things I can be absolutely certain they are undisputable facts. I give one example for some to ponder about.


    For all practical human purposes a fact is the truth of a matter as we can perceive it to be correct through the application of the six senses we are seemingly born with; they are; vision, smell, touch, hearing, taste, and, not very clear and precisely determined and understood, proprioception.

    However do not for a moment think or accept that a fact as perceived with our limited senses we have been born with is the end of the story, nor is it the beginning.

    Example: I am advanced enough in age to have gone to school in which I learned, almost axiomatically, that the atom was not fissionable. Hiroshima and Nagasaki have clearly elucidated the fallacy thereof. So much for the truth in a fact as it was once perceived as correct by us, human beings, in the near past.

    I shall demonstrate an example of a fact as I personally perceive it to be beyond question on this our Earth, our planet homeland;

    Barring the view of Arthur Schopenhauer that human intelligent comprehension is, in fact an illusion, we can look at the following example as a fact in the true, truthful position it encompasses.

    Therefore note; Excluding the average gestation period of approximately nine months of a human, from conception till birth of a new human being, life commences at the moment of physical birth. As a baby is born its birth is a fact, it has happened, it is there for all to see, to feel and to touch, for those who are inclined and in a position to do so. The event demonstrates an indisputable fact.

    This indisputable fact of the start of a human life is also an indisputable fact in that it is the commencement of the absolute unquestionable and certain way to death. There is no escape from this and after the split second of this hypothetical new life, measuring time in an astronomical time and place frame, all is over but the fact continues. There is nothing known by US beyond this life, in whatever form we may be capable of understanding the meaning of nothing.

    • Henk – An interesting argument in defense of indisputable facts. Before I tell you why I don’t totally agree, let me say that in practical human terms, I accept an uncountable number of things as firm fact. But I know some of those facts are going to turn out to be wrong and replaced with other facts.

      But let’s start out with your example of the birth of a child. Have you ever seen a child born? Even if you have, have you any way of knowing from sensory experience that all children are born this way? Of course not. None of us have. Most of what we call fact we accept because we believe what we are told. We are told that there is sensory proof that the world is round, even though we spend all our lives experiencing it as flat. We are told the earth goes around the sun, even though it looks to each of us as if the sun goes around us. We accept the shape of the continents based on what others have told us we see. I accept that the desk at which I am sitting as I write this is made of wood. I accept that the beans I bought from the supermarket today were sourced in Kenya. I accept all these things as fact. But as a matter of fact, what any single individual can him- or herself directly observe is very very small. Even in science, we accept that others have observed what they say they have. But occasionally they are either wrong or have even deliberately lied.

      So there are potential problems undermining the sensory foundation supporting the absoluteness of fact: sometimes our sensory experiences are erroneous. We see things that aren’t there, we misinterpret what we see (“it’s a bird, it’s a plane, it’s superman…). Sometimes we mistake dreams for reality, some cultures even teach that dreams are real, valid insights into another world. Most children believe their dreams are real. I remember quite clearly flying when I was a child. The only reason I don’t accept this memory as a fact is because so many other experiences convince me that this memory is incorrect. We can misinterpret depth and distance, sounds (was that a gun shot or a door slamming?), what things feel like (is it very hot or very cold to the touch?), etc.

      So though for sheer survival we cannot go around questioning the validity of every single experience we have day in and day out, though we must live with a certain amount of assumed certainty, nothing — and I mean absolutely nothing — is indisputably certain. Even as you read this, you may only be dreaming. Or maybe I am. Who knows?

      What do you think?


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