A hypothesis is a testable proposal — one that could come out false when checked.
Hypothesis A testable proposal that some observation could refute.
Step 1: Something to Notice
Watch first. The explanation comes later.
A claim that explains every possible outcome — whatever happens, the theory accounts for it — cannot be tested by any observation at all.
Why is explaining everything a weakness?
Step 2: Find Out
Isolate a single variable and note what the result then licenses you to claim.
Step 1 — Predict
Which is the stronger scientific claim?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
Testable means refutable
A claim compatible with every outcome cannot be tested by any of them.
Evidence supports or refutes
It never proves. Confirmations accumulate support; one solid refutation can end a claim.
A theory is the strong end of the scale
An explanatory framework that has survived testing and unifies many observations.
Theory A well-tested explanatory framework, not a guess.
And it stays open to revision
Newton’s laws were confirmed for two centuries and turned out to be a special case.
A theory that explains everything predicts nothing
A useful scientific claim rules something out. If no possible observation could contradict it, it cannot be tested, and being unfalsifiable is a weakness rather than a strength.
A theory is not a guess
In everyday speech a theory is a hunch. In science it is an explanation supported by a large body of evidence and repeatedly tested. The word means nearly opposite things in the two contexts.
Step 4: A Common Mistake
Lots of people think
“Science proves things true.”
Step 5: Why the Word "Theory" Causes So Much Trouble
The same idea somewhere new.
In ordinary speech a theory is a guess. In science it is the opposite end of the scale: an explanatory framework that has survived extensive testing and ties many separate observations together. Atomic theory, the theory of gravitation and the theory of evolution are all in that second category. The everyday sense of the word is the source of a great deal of confused argument, and the fix is simply to notice which sense is being used.
Step 6: Think It Through
Practice makes it stick.
Explains Everything
Problem 1 of 2
A claim accounts for every possible result. Is that a strength?
Two Senses of a Word
Problem 2 of 2
What does "theory" mean in science?
What Evidence Does
1 of 5
Does science prove theories true?
2 of 5
What makes a hypothesis scientific?
3 of 5
Newton’s laws were confirmed for two centuries. What happened?
4 of 5
Which claim is stronger?
5 of 5
Why is a confounded experiment worthless even with precise measurements?
Step 7: Quick Check
Show what you know.
Question 1 of 1
Does science prove things true?
Step 8: Explain It in Writing
Claim, evidence, then reasoning.
The question
Explain why science does not prove theories true, and why a theory that explains everything is weak.
Fill in all three boxes. The reasoning box is the one that matters most.
What You Found Out
- A hypothesis must be refutable by some possible observation.
- A claim that explains every outcome forbids nothing and tells you nothing.
- Evidence supports or refutes; it never proves.
- A scientific theory is a well-tested framework, not a guess.