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Evolutionary theory. M-theory. The general theory of realitivity. From the moment we begin schooling, we begin the process of learning about science, and the various theories which form it.

From flight to cancer research, much of what scientists research is based on groupings of evidence called a scientific theory. Whenever we launch a satellite into orbit or give someone medicine when they are sick, we are making use of a scientific theory. However, what is a theory? Why is there so much debate about theories, and why do some people say that some things are "just a theory" or "only a hypothesis" when scientists say otherwise?


The scientific lexicon, or word use, is different from what people use normally. For example, a theory outside of the scientific community is often a fuzzy or vague thing, something which we are not sure about. A good way to describe a theory that way is a "logical guess" at what is going on. But that is not how it works for scientists.​

The aim of this post is to provide a short look at some basic scientific terms which often come up in debates. This includes such terms as "scientific theory," "scientific law," "scientific method," "fact" and "hypothesis." Knowing what a scientist is talking about will help a bit in distinguishing what someone is actually saying. Few things halt a debate in good faith more completely than a language barrier.​

So what is a scientific theory?

A scientific theory is an inductive line of logical reasoning, based on empirical evidence, structured with scientific laws to produce meaningful and testable predictions and conclusions on topics within it's scope.​

Scientific theories are collections of tested hypotheses, observations and experimental results bound together into useful context. Theories are based on multiple lines of inquiry and evidence collected thereof, and are often quite extensive.​

The creation of a scientific theory is a profound achievement of scientific discovery and research. A fair bit more comprehensive than "just a theory."​

So... it's just a hypothesis itself, right?

No.​

A hypothesis is simply a proposed explaination for phenomena to predict outcomes. They are speculative or conjectural. They can be based on evidence or ideas from theories, but are not theories in and of themselves and have yet to be tested.​

To be a scientific hypothesis, it also has to be testable.​

When a hypothesis is called a "working hypothesis," that means it's been accepted provisionally. Hypotheses which have been tested generally form together to make up an overarching scientific theory, which in itself is also used to predict outcomes.​

The ability to predict outcomes correctly is the hallmark of a successful scientific theory, and is central to what they are. The same expectations do not exist for a hypothesis.​

Wait. Testable?

Science deals with what is falsifiable and what is testable. Whether or not God exists, for example, is not a scientific question which can be tested via the scientific method -- it cannot be tested since we cannot put God in a test tube.​

Scientific method?

According to the Oxford dictionary, it is the "systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses."​

For something to be considered scientific, measurable empirical evidence is studied to come to viable and logical conclusions to compare against suggested hypotheses. The method includes expectations to share data and calculations as part of peer review and for general access to provide barriers to bias and personal beliefs. This is so as to provide the ability for others to reproduce results, which is key to the scientific method.​




The above describes a potential path. As will be seen here, hypotheses do not directly become theories in and of themselves, and theories are not directly related to laws. While the above picture does describe it some people may mistakenly misinterpret them as a hierarchy, which they are not. They are different mechanisms as part of the overall scientific process, with different purposes.​

... so what is a fact, then?

A provable concept.​

So we know something for sure, then!

No.​

Proof is for alcohol and mathematics. In science, instead of proof, the term more commonly used is "overwhelming evidence."​

To be short: science is never absolute, and never 100% sure. Nobody can be sure, no process is infallible. But it's the best way for us to get close, and often scientific results are accepted as factual given the superior method they provide to obtain these results.​

Science attempts to explain the natural world, it does not state what is unequivocally. Hence, scientists do not "think they know everything," a common line of attack which is predicated on a mistake. Indeed, the scientific method adds on questions for every answer given. Readers who have done statistics know that achieving 100%, especially related to error and such in science, is impossible. Hence, there is always a bit of doubt in regards to even the most substantive body of evidence.​

However, this bit of doubt does NOT throw an entire theory into question, and is not basis alone for opinions contrary to scientific findings to be allowed because something is "just a theory." Theories are generally accepted as correct, and many are called facts. For a theory to be thrown into question, extensive contrary evidence must occur through the scientific method which cannot be explained through errors or shortcomings in the experiment itself.​

But evolution (for example) is a fact and a theory?

Yes. Scientific literature commonly calls evolution a theory and a fact. Sometimes, a theory can also be called a fact.​

A fact in science is an observable and verifiable observation. For example, if a ball is clearly red, we can state that the ball is red. Everyone capable of using the scientific method is capable of coming to the same conclusion. Scientic theories and hypotheses seek to explain or interpret facts.​

The idea of a "fact" in the scientific lexicon can at times be surprisingly abstract, and hence is a confusing term to use. Outside of the basic scientific use of facts, using the layman's term is a lot easier than trying to stay true to the scientific lexicon.​

When reading scientific literature, it is important to keep in mind that assumptions or assertion of facts are used as well.​




So what happens when a theory is disproven?

First off, the author of this ramble gets testy because someone used the word "proven."​

Theories which have been left by the wayside are called superceded theories, but often find use still in modern life because they are able to predict things successfully still. We still use Newtonian mechanics to describe the velocity of devices, for example. When building a house, we don't care about the curvature of the Earth.​

As scientific theories are based on empirical results and inductive reasoning, they can often still be successfully applied even if the underlying theory of such things as Newtonian mechanics can't keep up with the General Theory of Relativity.​

Then what are scientific laws?

A scientific law is the end point of the amalgamation of experimental results from repeated observation, and does not attempt to explain anything. They are simple verbal/mathematical statements about what is, or the relationship between two or more elements.​

Unlike theories, laws are limited only to what has already been observed. Hence, while scientific theories predict, laws regurgitate. A law is hence only useful in situations or tests already conducted many times before. Hooke's law, for example, can only be used in the same cases it was originally tested for and where that relationship holds true, and is a simple mathematical equation to identify a relationship -- a law does not posit what will happen otherwise.​

Unlike below, a scientific law most likely doesn't have a loophole which isn't already known.​





But I saw this scientist and he said...

People explaining things have to deal with a major roadblock, and that is the layman lexicon being different from the scientific lexicon. That assumes that they even speak the same language as us! It could be the difference was never taught, or it's easier to describe something in more absolute terms.​

It is, for example, easier to describe evolution as a fact, then to explain science is not absolute, or that science is a theory. Short hand explanations often leave a lot to be desired! Lines like "proving a theory" are sometimes simply much easier to use than otherwise, and it's not widely educated that the word proof is necessarily a bad one, even amongst scientists.​

... and sometimes, people simply make mistakes. Sometimes people paraphrase, and sometimes what a scientist said and what makes it through the middle man, be it a friend, a teacher or the media, is sometimes lost in translation.​


-------

I hope this helps. The point of this was to point out and describe briefly the differences between the common terms and the scientific terms, and to make people aware that differences do exist. It is a simple overview and should not be considered a complete explanation in and of itself -- more extensive versions can be found following a simple google search. Should any errors be noted, please report them!

A final note I would like to add is to remember that each field has their own lexicon. Sometimes simple words, innocuous in a sentence, can mean a great deal in different ways, so you must always be on guard and remember that you have a bias towards mainstream terminology. Complex concepts and so forth may not reflect the wording used to describe them as you understand the words.

Evolution is only an example. I did not intend this to be a debate on evolution.​

This guide has no future edits planned. Please do not send edit suggestions to this account.
 

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This is among the best posts I have seen on this site. It's nothing new to me, but I don't think I could have ever expressed this so clearly and thoughtfully. I have nothing really to add, I just hope that some of the "just a theory" crowd have the patience and desire to read and understand it all.
 

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Fantastic post! This should be archived somewhere so as not to be lost, and/or made into an article.

For those of us who are philosophically inclined, I'd like to add this:

Philosophy of Science Archive (Internet Encyclopedia of Philosophy)

Some particularly important articles from there:

Confirmation and Induction*[Internet Encyclopedia of Philosophy]
Evidence*[Internet Encyclopedia of Philosophy]
Models*[Internet Encyclopedia of Philosophy]
Laws of Nature*[Internet Encyclopedia of Philosophy]
Theories of Explanation*[Internet Encyclopedia of Philosophy]
 

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Ideally, it would be a sticky somewhere like the debate forum, where lack of understanding of terms is rife, and major cause of stupid arguments.
 

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great post and great explanation. I imagine there are a lot of theories that are currently untestable, and will be for a long time. String theory is one that comes to mind. Do you have an example of a theory that was widely accepted in the scientific community that failed once it was possible to test it?
 

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Do you have an example of a theory that was widely accepted in the scientific community that failed once it was possible to test it?
Possibly Lamarckian inheritance. This was the idea that parents acquire traits during their lifetimes and then pass those traits along to their children: eg, a man who works as a blacksmith will become big and burly, and so he will have big and burly children. Or that giraffes' necks stretch out during their lifetimes because they're always reaching for leaves, and so they have children with successively longer necks. I think Lamarckism was ultimately discredited by Gregor Mendel with his peas, although something similar is starting to resurface in the field of epigenetics.
 

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Also worth noting, in the spirit of the thread: strictly speaking, there's no such thing as a theory that's widely accepted before it's possible to test. Given that theories are condensations of observations and testable hypotheses, a theory can't be formed until the hypotheses that compose it can be tested. So in my example, Lamarckian inheritance was actually a hypothesis, not a theory. It was a testable, tentative explanation for observable facts (that children tend to carry traits from their parents); but because it couldn't be adequately tested, it remained a hypothesis.
 
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[strictly speaking, there's no such thing as a theory that's widely accepted before it's possible to test]
I'm not sure if string theory is considered widely accepted in the scientific community, but it certainly gets a lot of attention and seems to be getting a fair amount of acceptance from respected physicists. While at the same time, other respected scientists consider it "philosophy" at this point. This is a theory that is a long way from being tested, yet many universities are now offering courses on string theory in their science departments. Things like this just make it all more confusing.
 

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I'm not sure if string theory is considered widely accepted in the scientific community, but it certainly gets a lot of attention and seems to be getting a fair amount of acceptance from respected physicists. While at the same time, other respected scientists consider it "philosophy" at this point. This is a theory that is a long way from being tested, yet many universities are now offering courses on string theory in their science departments. Things like this just make it all more confusing.
String "Theory" is a bit of a misnomer. A theory is basically just a hypothesis that gained backup by empirical evidence. In case of String "Theory" the latter is still missing.

Anyway, String Theory has received a very mixed reaction in the theoretical physicist community. There are scientists who argue that it is inherently untestable, i.e. unscientifitic. Renounced scientists like Lee Smolin think that string theory is indeed a dead end. Guys like Ed Witten (arguably the greatest theoretical physicist of our age) have spend years remodeling string theory (in his case into M-Theory) and obviously believe that it is a viable option. So, there is no general consens on the topic.

Basically, what makes a few physicists partial to it, is, that it provides a theoretical model that describes the 4 main forces (electrmagnetism, weak force, strong force and gravitation) in a succint concept. So far physicists made contributions to understand 3 main forces as a unified model, except gravity. As of now, we have no theory that can unifiy general relativity and quantum mechanics/quantum field theory.

As string theory seems to provide this unification, it has been pursued and endorsed by many notable physicists. However, this does not imply that it is correct. It is indeed strange that a hypothesis, that has been around for decades remains untested. And a test would be the main objectve to discern the validity of it. Perhaps it is really just a dead end.

Stuff like higher dimensions may be beyond humans grasp to falsify. There was actually an experiment conducted in CERN that ought to test wether higher dimensions might have some sort of "effect" on "our" dimensions. It was negative and is deemed by some scientiest as the sole empirical test String Theory has faced (and failed). All in all the situation with the testabilty of string theory is a major concern for physicists. Providing hard evidence for or against it, might change the landscape of modern physics.

And if you want to explore String Theory try Barton Zwiebachs "A first course in string theory". Most textbooks about string theory are graduate level stuff and deman a myriad topics of higher mathematics like algebraic topology. I haven´t read that much of this text, but it seems very accessible for anyone with a moderate knowledge in undergraduate math/physics. It is generally considered the easiest introduction.
 

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It's easier to find widely accepted theories that proved false if you go back further in time....basically all of ancient Greek science has been replaced. But the feed-back loops in the scientific method (well shown in the diagram) make this increasingly less likely.

That's not to say we are converging on the Truth of the Universe but merely that most of what we know gains more credibility as we add more self-consistent knowledge to the system.

So the more modern tendency ...in the more formally developed sciences....is not so much to replace theories as much as to supersede them. In the less formal sciences like biology and especially in the "soft" social sciences you will still find turnover.

For instance neurobiology is a field filled with unwarranted assumptions (conjectures) such as the "fact" that the mental representation of objects of perception is rooted in the neurochemistry of the brain. You see this commonly in the "chemical imbalance" theory of just about every major mental disorder -- great theory for the drugs companies though.

In fact it is unknown how the brain represents these states....on the level of neurons, systems of neurons, virtual "programs" running on the neural substrate, some kind of sub-cellular QM mechanism, etc. Yet much of psychology and medicine is being built upon this bed of sand.

Another example is in the field of Paleoanthropology. There have been several competing theories on the evolution of humanity. Molecular biology started to add data to this field in the 90s which overturned some previously widely held ideas. There is still much debate but it seems the "out of Africa" hypothesis is the current consensus.
 

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String "Theory" is a bit of a misnomer. A theory is basically just a hypothesis that gained backup by empirical evidence. In case of String "Theory" the latter is still missing.

Anyway, String Theory has received a very mixed reaction in the theoretical physicist community. There are scientists who argue that it is inherently untestable, i.e. unscientifitic. Renounced scientists like Lee Smolin think that string theory is indeed a dead end. Guys like Ed Witten (arguably the greatest theoretical physicist of our age) have spend years remodeling string theory (in his case into M-Theory) and obviously believe that it is a viable option. So, there is no general consens on the topic.

Basically, what makes a few physicists partial to it, is, that it provides a theoretical model that describes the 4 main forces (electrmagnetism, weak force, strong force and gravitation) in a succint concept. So far physicists made contributions to understand 3 main forces as a unified model, except gravity. As of now, we have no theory that can unifiy general relativity and quantum mechanics/quantum field theory.

As string theory seems to provide this unification, it has been pursued and endorsed by many notable physicists. However, this does not imply that it is correct. It is indeed strange that a hypothesis, that has been around for decades remains untested. And a test would be the main objectve to discern the validity of it. Perhaps it is really just a dead end.

Stuff like higher dimensions may be beyond humans grasp to falsify. There was actually an experiment conducted in CERN that ought to test wether higher dimensions might have some sort of "effect" on "our" dimensions. It was negative and is deemed by some scientiest as the sole empirical test String Theory has faced (and failed). All in all the situation with the testabilty of string theory is a major concern for physicists. Providing hard evidence for or against it, might change the landscape of modern physics.

And if you want to explore String Theory try Barton Zwiebachs "A first course in string theory". Most textbooks about string theory are graduate level stuff and deman a myriad topics of higher mathematics like algebraic topology. I haven´t read that much of this text, but it seems very accessible for anyone with a moderate knowledge in undergraduate math/physics. It is generally considered the easiest introduction.
My whole department is -devoted- to these beautiful but scientifically unprovable theories.
We even named the department after them!: Mathematics :cool:

But seriously the down side of string theory that I see is for graduate students who get caught up in it and are left holding the bag when (if) it finally gets shot down or grinds to a halt because of lack of progress.

But this kind of style of theoretical physics....using mathematical beauty as an Ansatz....it has worked before albeit in much more conservative contexts.
 

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My whole department is -devoted- to these beautiful but scientifically unprovable theories.
We even named the department after them!: Mathematics :cool:
Lol. Hey, nothing against mathematics. I love me some topology and real analysis.

But on a serious note, mathematics itself does not make statements about nature. Once you have a priori proven a mathematicatal conjecture, via the stringent use of logic and a basis of evident axioms, it is enough to show that the conjecture is true. String theory might display inner stringence, but this does not matter as far as it claims pertain to the empirical world. I personally will not grant string theory anything until it comes up with potential experiments to make it testable.

If I may ask, in which field of mathematics did you specialise?

But seriously the down side of string theory that I see is for graduate students who get caught up in it and are left holding the bag when (if) it finally gets shot down or grinds to a halt because of lack of progress.
Yup. That is the number one reason why I will not specialise in string theory. Quantum Gravity on the other hand has a lot of potential (no pun intended). (OK, it was a pun and the only reason I brought it up was to make a pun)

But this kind of style of theoretical physics....using mathematical beauty as an Ansatz....it has worked before albeit in much more conservative contexts.
Zombie-Dirac? Nah seriously, I can see what you mean. Theoretical physics has to entertain seemingly unlikely and speculative ideas all the time. Even though many of them turned out to be wrong, they might haven given rise to better models, one way or another. I have to think of Weyls unified field theory which turrned out to make heavily inaccurate predictions and was soon discarded, but turned out to use an approach that happened to be suitable for quantum field theory.

I am afraid that string theory is more metaphysics then physics.
 

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So a scientific theory does not necessarily affix an idea firmly in the field of science for some scientists. I asked a physicist once if time could "possibly" be a construct of life. To him, this wasn't even a question for a scientist to even consider. He said that was a philosophy question. Yet string theory and the possibility of a holographic universe seem to be open to discussion amongst scientists now. I personally think the idea of "time being a construct of life" would fit very neatly into both of those ideas. I guess my problem with science is that there doesn't seem to be clear boundaries on topics of discussion...and different scientists seem to have different boundaries. Hmmm...which forum should I post this question in :)
 

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So a scientific theory does not necessarily affix an idea firmly in the field of science for some scientists. I asked a physicist once if time could "possibly" be a construct of life. To him, this wasn't even a question for a scientist to even consider. He said that was a philosophy question. Yet string theory and the possibility of a holographic universe seem to be open to discussion amongst scientists now. I personally think the idea of "time being a construct of life" would fit very neatly into both of those ideas. I guess my problem with science is that there doesn't seem to be clear boundaries on topics of discussion...and different scientists seem to have different boundaries. Hmmm...which forum should I post this question in :)
The difference is that string theory is a hypothesis based on observation, that makes predictions, and is, in theory, falsifiable. The idea that time is a construct of sentience offers absolutely nothing, other than philosophical musing.
 
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