What are the strengths and the limits of the scientific method?
I’m a professor of astronomy, and I think the scientific method is wonderful.
It has given us antibiotics, airplanes, and Moon landings. It has revealed to us why stars shine,
and how cells function. Every day, and all around the globe, it continues to enable new discoveries,
peering deeper into workings of the material universe.
But all this success could tempt us to think that the scientific method
is the only valid method to gain knowledge; that it can be used not only to explore matter, energy,
molecules, and cells, but also morals, politics, and the supernatural realm.
We should resist this temptation, because it completely misunderstands
what the scientific method can and cannot do.
Why has the scientific method been so successful when applied to some aspects of reality,
and not to others? To answer this we must first look closer at what the scientific method is.
The classical description of the scientific method is that our inquiry starts with a question.
Since I’m an astronomer, let’s take an example from astronomy:
from where do the Sun and the stars get their energy to shine?
The next step is the formulation of a hypothesis.
Perhaps we use our everyday experience to hypothesize that the Sun is like a big candle,
and gives off light due to the conversion of one kind of molecule with a lot of stored energy,
such as candle wax, into molecules with less stored energy such as carbon dioxide.
This hypothesis then leads to a prediction. If the Sun’s radiance is due to a chemical conversion
from one molecule to another, and if you know what is the maximum energy stored in molecules
as well as the age of the Sun, we could predict how massive the Sun would have to be
to be able to radiate light at its current rate.
The next step is an experiment or observation to test this prediction.
In our case, we would measure the mass of the Sun. If we do this we would find
that the mass of the Sun is much too small for our hypothesis to be true.
The Sun cannot be generating light the same way as a candle does.
But perhaps this would inspire us to come up with a new hypothesis:
that the Sun is not powered by the conversion of one molecule into one another,
but rather by converting one atom into another through fusion.
If we took this idea, and went through the same steps as we did with the candle hypothesis,
we would find that the mass of the Sun fits with our new prediction.
This agreement between prediction and data doesn’t amount to proof
that the Sun is powered by fusion of elements --there might be other explanations that fit
the data equally well -- but we could say that your new hypothesis is supported by observations.
If a hypothesis has been consistently supported by many observations and experiments
and covers a general enough process, for example,
how the Sun and stars generate radiation, it is referred to as a scientific theory.
Because of the kind of knowledge it is, a scientific theory doesn’t give us the
same degree of certitude as we can get from a mathematical calculation
(like 2+2=4) or as can be generated by a valid logical syllogism.
In the scientific project, we frequently evaluate our theories against our observations,
and sometimes we discover that a theory needs to be refined or revised in the light of new data.
Why has the scientific method been so powerful in elucidating truths about nature
and harnessing its powers for technical development?
A large part of the answer is its empiricism. When applying the scientific method,
ideas and hypotheses are constantly tested against observations and experiments.
This means that ideas that do not conform to reality will be discarded, while ideas that
do correspond to the true nature of things will keep passing observational and experimental tests.
In practice the scientific method is somewhat more complicated. The outcome
of an observational or experimental test of a hypothesis is often not completely obvious,
and requires interpretation by a scientist. This interpretation will depend on what other
scientific theories the scientist has accepted as true, and also on other presuppositions
that more properly belong to what St. Thomas Aquinas would call the philosophy of nature.
As a result new scientific theories, such as heliocentrism or the Big Bang theory,
sometimes take longer to gain acceptance in the scientific community
than a mechanical application of the scientific method would suggest.
What are the limits of the scientific method?
Following the scheme above, it relies on measurements and on repeatability.
Measurements are at the core of the scientific method; this is how we test if a hypothesis
agrees or disagrees with the objective reality. And that is also a limitation: If a process or
a thing cannot in principle be measured it cannot be investigated using the scientific
method. And there are things -- even some very important things -- that we cannot measure.
For example, you cannot scientifically measure how much your spouse loves you.
Such information can only be gotten through testimony and trust of that testimony. You
also cannot use the scientific method to determine the morality of a certain action,
or prove or disprove God’s existence. (We’ll come back to this in a later video.)
Even among things that are measurable, not all are subject to the scientific method, like miracles.
Miracles fail the second criteria of repeatability.
We'll also have a whole video on that subject later.
Finally it is worth noting that the scientific method is not independent
of other sources of knowledge. The scientific method relies on certain assumptions of the
cosmos, such as: that it is orderly and intelligible.
It presumes that we have access to objective truths through observations and experimentation.
And it relies on an assumption that our reason is ordered towards identifying truths,
that is, that we can recognize when our ideas correspond to reality. None of these can be
scientifically proven, and without any of these, the scientific project just would not work.
The scientific method has been wonderful at advancing our understanding of the
material universe, but it is far from the only source of knowledge.
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