Sceptical Thinking 2 : The Scientific Method

In my introductory post, I explained a couple of reasons why I think that we could all benefit from being sceptical. In this post I shall begin to look at one of the main ways you can begin to engage in sceptical thinking. Being a sceptic isn’t something that you can do a degree in (at least not that I’m aware of), its something that you have to teach yourself. It’s not something that becomes instantly apparent either; I am a self professed sceptic, yet I still catch myself thinking irrationally and believing things on insufficient evidence. Learning to be a sceptic is not about instantly purging your mind of all false beliefs, it merely provides a good means of spotting them, and examining them.

One of the cornerstones of scepticism is the scientific method. Learning about what science is and how it works, familiarizing yourself with what is and what is not scientific will automatically give you some valuable methods of sceptical thinking. So without further a do, I shall introduce the scientific method, and explain how science works.

Hypotheses/Null Hypotheses

When a scientist has an idea they begin by formulating a hypothesis. A hypothesis gives a concise statement of what you should expect to find if your idea is true. They follow a simple formula – which you’d do well to memorize – a hypothesis is an ‘if…..then….’ statement.  For example you might think that pH levels will affect the growth of plants, so in order to make this idea a hypothesis, you’d write it as follows: if pH levels affect the growth of plants then plants grown in soil of a different pH will show differences in growth.  A null hypothesis is quite simply the opposite of the hypothesis, so in this case the null hypothesis would be: if pH levels do not affect the growth of plants then plants grown in soil of a different pH will show no significant differences in growth.

Hypotheses help us think sceptically because it helps us to understand what kinds of evidence we might expect to find for a particular claim. Its a useful starting point when thinking about claims. If you formulate them into hypotheses then you can start to get an idea of the kinds of evidence you’d need to support them. Try it out for yourself, take a sheet of paper and write various claims on it, ‘if aliens really are abducting humans then… (followed by what you’d expect to find if this were true)’ for example (you can come up with more than one hypothesis for the same claim) – this is a good exercise in both scientific and sceptical thinking.


The hypothesis/null hypothesis form the backbone of one of the most important aspects of science; the experiment. Once you have come up with your hypotheses (you can test more than one in the same experiment) you can then use them to build an experiment. Continuing with with example of the effect of pH on plant growth you could take a number of different plant pots, fill them with a range of different soils all with a different pH level (making sure to record them!), then grow a plant in each of them. Now you need to make sure that all of the plants are the same, and that they are grown under the same conditions (the same levels of light and so on) – this is important because you are only measuring the effect of pH, so you don’t want any other variables effecting your results. Keeping the conditions the same, apart from the thing that you are measuring the effect of is important – and it is something you need to bear in mind when analysing evidence. Did they conduct their experiment accurately? Is there some other factor that might influence the results?

Once you’ve conducted your experiment, you collect your results, in this case measurements of leaf area, and plant height/width and so on. You then conduct various analyses on your results, such as making graphs to show any trends, or performing statistical analyses (which I shall not bore you with here, although it is useful to know a bit about stats as a sceptic).

Once you’ve analysed your results you should be able to see whether your experiment disproved (or falsified) the null hypothesis. Why do we attempt to falsify the null hypothesis rather than prove the hypothesis correct? Because there is no way to conclusively prove something right, you can only ever say that it hasn’t yet been proven wrong, you can prove something wrong however, so therefore, your experiment (if you do notice that pH affects how plants grow) will have falsified the null hypothesis (if pH levels do not affect the growth of plants then plants grown in soil of a different pH will show no significant differences in growth) and provided evidential support to your hypothesis.

We learn from how experiments are set up, the ways in which we control them teach us about how we should meticulously scrutinize all the factors which might affect an outcome, the ways in which we analyse the results tell us what is and what is not a reasonable deduction from a certain set of data. Scientific experiments are a way of putting our ideas to the test – which is what scepticism is all about. If your experiment fails to support your hypothesis then it’s back to the drawing board.

So if you did write a list of hypotheses, underneath them try to devise a way in which you might be able to test them with an experiment (you don’t actually have to do the experiment, so it can be as wild and expensive as you like) bearing in mind what it is you’re trying to test, and how you’d account for and eliminate other factors which might affect your results. If you really struggle with some then you might well have posited an un-testable claim – which isn’t a bad thing it’s really handy to know what one of those looks like. If a claim cannot be tested scientifically then it is essentially worthless, and the best you can say of it is ‘it might be true, or it might not, there is no way of finding out’.

Peer Review

Once you’ve conducted your experiment and you wish to publish it, the publisher will send your paper off to be scrutinized by experts in the relevant fields. So in our case it might be sent to a botanist, a soil expert, a biochemist etc. They would then meticulously go through your paper looking for mistakes and errors which you may have overlooked. You may for example, have chosen a species of  plant which is unusually sensitive to pH, or overly insensitive to it, or perhaps you missed off an important part of your method which may have affected your results; such as neglecting to mention how you watered the plants, and whether it was done at the same time for all the plants, with the same amount of water.  The purpose of peer review is to spot things that you may have missed, to look for errors etc.

This teaches us two important lessons. Firstly you should be very weary of people putting forth scientific papers that have not gone through peer review, go and check out the journal and see whether or not they are peer reviewed, if not then there is reason to doubt the legitimacy of the paper. Secondly, you should always remember that a second opinion is extremely valuable, and that you should welcome open critiques of your ideas, if you don’t do so, you might overlook something rather important.


Once many papers have been published on a particular subject – in this instance the effect of pH on plant growth, the evidence in these papers can be used to formulate a theory. Data might come from biochemists analysing the effect of pH on plant cells, from ecologists studying the pH of soils out in the field, etc. Once this data is collected, scientists start to think of a theory for how pH affects plants. A theory is a coherent explanation of a set of related facts and observations.

A theory will then provide a framework for future experiments because they make certain predictions which can be tested with new hypotheses. A theory’s strength is tested by how consistently it meets predictions. The theory of evolution by natural selection for example, has been tested by new evidence for over 150 years now, and it has consistently met all it’s major predictions. A theory of this stature is as close as we can come to truth in science.

When people state ‘that’s just a theory’ in relation to some scientific idea or other, they simply do not understand, or rather are dishonestly mistaking the meaning of theory in a scientific context. Whilst it is true that ‘theory’ in a colloquial sense implies a guess, a scientific theory is anything but. The theory of evolution was not dreamed up as a vague guess, it is an extremely coherent explanation of all the facts that we have so far encountered in biology. Swapping the scientific definition of theory with the colloquial definition is a fallacy of equivocation and does not hold any weight as an argument.


So in summary what can we learn from science? Firstly we learn how to put claims to the test – getting an idea of how to find out if something is true or not is very important as a sceptic. We also learn to be meticulous, thinking about all the different kinds of variables which may affect outcomes. We learn what conclusions are reasonable to draw from a certain set of data, the importance of opening your ideas up to scrutiny.

Science is not completely perfect, but it is the best means we have for finding things out. As a sceptic you should try to think about the world as a scientist. Rather than believing things because it would be nice if they were true, try to examine all things and reject those hypotheses that do not stand up to scrutiny.



Filed under Critical Thinking, Science

2 responses to “Sceptical Thinking 2 : The Scientific Method

  1. Who knew you could make a blog on the scientific method this interesting and fun to read? 🙂

  2. Concerned Scientist

    “Swapping the scientific definition of theory with the colloquial definition is a fallacy of equivocation and does not hold any weight as an argument.”

    You confuse theory with theorem, and you would equate the former with the latter. Truly, it holds great weight as an argument, watch this: prove to me how evolution is demonstrable in a laboratory?

    In order to avoid semantics, let’s be clear. Genetic anomalies and natural selection do not prove evolution from a common ancestor. These are observable but the theory of evolution is not.

    Basically, you may as well have entitled this article “Scientism and Positivism”.
    I don’t study the Theory of Biochemistry and the Theory of Microbiology, I study Microbiology and Biochemistry. Your agenda in thus regard is pathetically obvious. Please read some more on scientism/positivism, and their shortfalls.

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