

Ask HN: What's the difference between a theory and a fact? - solipsist

Can a theory ever become a fact? Or are they in two completely different areas, so one can never become the other?<p>For example, was gravity ever a theory (assuming it's a fact now)?
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psyklic
First of all, gravity is not a fact; it is a theory. To be more precise, it is
a fact (only in casual terms) that "on the surface of Earth in free air, if I
drop something it will fall to the ground." (Note this statement is still not
always true.) However, WHY this occurs is a theory. So by "gravity" here I am
referring to this why -- the "theory of gravity."

Theories are abstract and conceptual, and they are never known to be correct
or incorrect. Rather, we build a corpus of evidence for or against them -- we
never know their validity 100% for sure. For example, at any point in the
future, we may find some piece of evidence which disproves gravity as we know
it. Then, we will be forced to revise our theory of gravitation (e.g. when
general relativity was discovered).

A fact is something that is 100% true. If I say that "Sacramento is the
capital city of California," then this is a fact because we defined it that
way.

It could be that the theory of gravitation is 100% true and hence a fact.
However, we will never know this, so to us it will always be a theory.
Sometimes, people feel so sure about a theory that they go ahead and call it a
"fact" or a "law" -- but this just indicates that a lot of evidence supports
it and hopefully no evidence (yet) invalidates it; it is still a theory. (So
to be precise, my original "fact" about dropping something is really a theory
with LOTS of evidence!)

So to answer your question, a theory can be correct or incorrect. If it is
correct, then it is also a fact. However, we will never know 100% whether it
is correct, so to be precise we should continue to call it a theory.

~~~
rick_2047
If this is how you define theory, how would you define hypothesis?

~~~
orls
A hypothesis is any testable, falsifiable conjecture. I can hypothesize that
gravity is negative at one particular spot in your back garden.

As I understand it, a theory is any hypothesis that is believed to hold (at
least for now, under the conditions it's thus far tested under, or based on
the evidence we already have). In other words, a theory is a hypothesis that
is _provisionally_ considered true.

Thus, my hypothesis about your back garden could turn into a general theory of
conditions under which gravity turned negative, if observations were made
which supported it (which is, admittedly, unlikely!).

I'd agree with the Sacramento example above, i.e. that the only things we can
consider facts are things that we've agreed upon/defined. This is a smaller
set of things than people normally call facts.

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zmmz
Please don't take this in an offensive way, but there are other communities
where such a question would be more appropriate.

As a starting point, I can recommend you check out lesswrong.com, you can find
their "introductory reading" here: <http://wiki.lesswrong.com/wiki/Sequences>
the first item on the list deals exactly with the question you have posed:

<http://yudkowsky.net/rational/the-simple-truth>

Happy reading!

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Animus7
A theory is a suggestion of some truth (in the logical sense). A fact is a
theory that has been "proven".

How a theory can come to be (or needs to be) "proven" to become a fact is more
of a philosophical question than anything else, and if the schism between
religion and atheism is any indication, it's a contentious one that I
generally prefer to stay away from arguing.

