The **hypothetico-deductive model** or **method** is a proposed description of scientific method. According to it, scientific inquiry proceeds by formulating a hypothesis in a form that could conceivably be falsified by a test on observable data. A test that could and does run contrary to predictions of the hypothesis is taken as a falsification of the hypothesis. A test that could but does not run contrary to the hypothesis corroborates the theory. It is then proposed to compare the explanatory value of competing hypotheses by testing how stringently they are corroborated by their predictions.

One example of an algorithmic statement of the hypothetico-deductive method is as follows:^{[1]}

. Use your experience: Consider the problem and try to make sense of it. Gather data and look for previous explanations. If this is a new problem to you, then move to stepÂ**1**.**2**. Form a conjecture (hypothesis): When nothing else is yet known, try to state an explanation, to someone else, or to your notebook.**2**. Deduce predictions from the hypothesis: if you assumeÂ**3**is true, what consequences follow?**2**. Test (or Experiment): Look for evidence (observations) that conflict with these predictions in order to disproveÂ**4**. It is a logical error to seekÂ**2**directly as proof ofÂ**3**. Thisformal fallacy is called**2***affirming the consequent*.^{[2]}

One possible sequence in this model would be * 1*,

*,*

**2***,*

**3***. If the outcome of*

**4***holds, and*

**4***is not yet disproven, you may continue with*

**3***,*

**3***,*

**4***, and so forth; but if the outcome of*

**1***shows*

**4***to be false, you will have to go back to*

**3***and try to invent a*

**2***, deduce a*

**new 2***, look for*

**new 3***, and so forth.*

**4**Note that this method can never absolutely **verify** (prove the truth of) * 2*. It can only

**falsify**

*.*

**2**^{[3]}(This is what Einstein meant when he said, “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”

^{[4]})

Despite the philosophical questions raised, the hypothetico-deductive model remains perhaps the best understood theory of scientific method.