# Mental Model: Scientific Method

by on December 23, 2009

The scientific method refers to a process of thought based on integrating previous knowledge, observing, measuring, and logical reasoning.

Introduction to the scientific method (from wikipedia)
Since Ibn al-Haytham (Alhazen, 965–1039), one of the key figures in the development of scientific method, the emphasis has been on seeking truth:

Truth is sought for its own sake. And those who are engaged upon the quest for anything for its own sake are not interested in other things. Finding the truth is difficult, and the road to it is rough. How does light travel through transparent bodies? Light travels through transparent bodies in straight lines only…. We have explained this exhaustively in our Book of Optics. But let us now mention something to prove this convincingly: the fact that light travels in straight lines is clearly observed in the lights which enter into dark rooms through holes…. [T]he entering light will be clearly observable in the dust which fills the air.

The conjecture that “light travels through transparent bodies in straight lines only” was corroborated by Alhazen only after years of effort. His demonstration of the conjecture was to place a straight stick or a taut thread next to the light beam, to prove that light travels in a straight line.

Scientific methodology has been practiced in some form for at least one thousand years. There are difficulties in a formulaic statement of method, however. As William Whewell (1794–1866) noted in his History of Inductive Science (1837) and in Philosophy of Inductive Science (1840), “invention, sagacity, genius” are required at every step in scientific method. It is not enough to base scientific method on experience alone[6]; multiple steps are needed in scientific method, ranging from our experience to our imagination, back and forth.

In the twentieth century, a hypothetico-deductive model for scientific method was formulated (for a more formal discussion, see below):

1. Use your experience: Consider the problem and try to make sense of it. Look for previous explanations. If this is a new problem to you, then move to step 2.
2. Form a conjecture: When nothing else is yet known, try to state an explanation, to someone else, or to your notebook.
3. Deduce a prediction from that explanation: If you assume 2 is true, what consequences follow?
4. Test: Look for the opposite of each consequence in order to disprove 2. It is a logical error to seek 3 directly as proof of 2. This error is called affirming the consequent.

This model underlies the scientific revolution. One thousand years ago, Alhazen demonstrated the importance of steps 1 and 4. Galileo (1638) also showed the importance of step 4 (also called Experiment) in Two New Sciences. One possible sequence in this model would be 1, 2, 3, 4. If the outcome of 4 holds, and 3 is not yet disproven, you may continue with 3, 4, 1, and so forth; but if the outcome of 4 shows 3 to be false, you will have go back to 2 and try to invent a new 2, deduce a new 3, look for 4, and so forth.

Note that this method can never absolutely verify (prove the truth of) 2. It can only falsify 2.[8] (This is what Einstein meant when he said “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”[9]) However, as pointed out by Carl Hempel (1905-1997) this simple Popperian view of scientific method is incomplete; the formulation of the conjecture might itself be the result of inductive reasoning. Thus the likelihood of the prior observation being true is statistical in nature [10] and would strictly require a Bayesian analysis. To overcome this uncertainty, experimental scientists must formulate a crucial experiment, in order for it to corroborate a more likely hypothesis.

In the twentieth century, Ludwik Fleck (1896–1961) and others found that we need to consider our experiences more carefully, because our experience may be biased, and that we need to be more exact when describing our experiences.[11] These considerations are discussed below.

The history of the scientific method (from wikipedia)
The history of scientific method is a history of the methodology of scientific inquiry, as differentiated from a history of science in general. The development and elaboration of rules for scientific reasoning and investigation has not been straightforward; scientific method has been the subject of intense and recurring debate throughout the history of science, and many eminent natural philosophers and scientists have argued for the primacy of one or another approach to establishing scientific knowledge. Despite the many disagreements about primacy of one approach over another, there also have been many identifiable trends and historical markers in the several-millennia-long development of scientific method into present-day forms.