"By doubting we come to inquiry; by inquiring we perceive the truth."
-Peter Abelard
Do not believe in anything simply because you have heard it. Do not believe in anything simply because it is spoken and rumored by many. Do not believe in anything simply because it is found written in your religious books. Do not believe in anything merely on the authority of your teachers and elders. Do not believe in traditions because they have been handed down for many generations. But after observation and analysis, when you find that anything agrees with reason and is conducive to the good and benefit of one and all, then accept it and live up to it.
-The Buddha
| Crick's Central Dogma |
That rigorous process is known as the scientific method, and the most important component of the scientific method is hypothetico-deductive reasoning (Sorry for the Big Word; I try to avoid them, but this one is too important).
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| Figure 1: Hypothetico-deductive reasoning |
Hypothetico-Deductive Reasoning
Hypothetico-deductive reasoning, in turn, is loosely based on deductive reasoning. Deductive reasoning works by discovering something new based on two or more facts you already known to be true. If A=B and B=C, then A=C. Deductive reasoning can be performed mentally without evidence from nature to support the argument. It works quite well for geometry and simple questions.Hypothetico-deductive reasoning, on the other hand, provides an extra step to support the new knowledge and is quite handy when you need to confirm or challenge a belief or claim.
To use it, first start with a central claim and call it the hypothesis. This hypothesis is then used to develop a model or method to test it's validity. Usually this method is in the form of a controlled experiment, but not always (figure 1). Now in most situations, you generally don't start with the hypothesis. You usually need to do some background research to formulate a workable (testable) hypothesis, and now-a-days, convince people to fund your research (figure 2).
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| Figure 2 |
If you are a medical researcher and you want to find out if acupuncture induces fertility, you can do an experiment to test it (or to spare yourself the effort and money, you can read about other people who did this experiment already). These types of controlled experiments can be complicated and expensive, but they generally involve treating to groups of randomly selected patients, one with the treatment to be tested and one with a placebo, and comparing the results. They yield reliable, objective, and predictable results when done properly.
We don't always have the luxury of conducting controlled experiments, however, so we often have to rely on lesser methods. If we wanted to know if smoking causes cancer for example, we could not ethically experiment on people, since that would involve randomly subjecting a group of people to take up smoking, but we can use 'observational studies' instead. We can, for example, find a group of people who already smoke and compare their health and their eventual fate with non-smokers. If we notice that the smokers developing cancer at a higher rate than non-smokers, that would lead us to think that there is a relationship between smoking and cancer. We can not be absolutely sure, however, because there may be a unknown variable that causes cancer as well as drive people to take up smoking: stress, poverty, etc. We can often make up for the deficiency of a controlled experiment by observing other predictable phenomena that would help support the smoking/cancer connection: laboratory studies on animals or cell cultures, for example. Building support for a claim can and often comes from more then one experimental source. If we know the biochemical mechanism that explains the development of cancer cells from particles in smoke that would help too.
Use your Critical Thinking Skills Wisely
This tool, this ability to detect if a claim is true or just speculation, is an important, life-saving, career enhancing, and even spiritually uplifting tool. It is like the Force to a Jedi knight. Use it wisely, and often. The next time someone shares a news article with you on Facebook about a new study that claims to have found the cause of autism, for example, question it! You don't have to actually do the experiment yourself, or even completely understand the study, but there are certain clues to look out for. Thanks to the magic of hyper-linking, you can often click right to the published study from the questionable article. Find out what kind of study was conducted. Not all studies are equal. First, make sure it's an actual study.Yes, sometimes researches will actually do what's called a literature review, where the researches find a bunch of older studies, make a logical connection to draw a conclusion, or hypothesis rather, but do not provide any empirical support for it. Recently (April 2012), such a literature review connecting autism with high fructose corn syrup (HFCS) was published in the journal Clinical Epigenetics and this paper was toted in the popular press as ground-breaking research. Both autism and HFCS are hot topic these days, so of course people are going to be excited about it. But on further review, the connection appears to be suspect; hypothetical at best.
Other things to look for: was this a 'controlled' experiment or was it based on 'observational studies'? Was it a study done on laboratory animals, or human subjects? Were the subjects randomized? Of course, like the evidence linking smoking to lung cancer, not all truths are going to be revealed by ideal randomized controlled studies, but sometimes you need to accumulate evidence from 'lesser' studies and clear reasoning. Truth is a slippery critter.
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| Figure 3: Inductive Reasoning |
Inductive Reasoning
Sometimes we don't need to use an experiment in the conventional sense, but can merely rely on observations for certain ideas. We know that white light is a combination of all other colors of light because when white light is passed through a prism, it separates into all other colors of light on the way out, whereas light of one color goes through a prism without changing. Nevertheless, whether we use a controlled experiment or simple observation, we are engaged in a dialogue with nature. The application of using nature to confirm our idea, or hypothesis, is referred to as empirical evidence, or simply empiricism.Empiricism plays an even more important role in another type of reasoning known as generalization or argument by analogy. When you generalize, you are actually engaged in a type of reasoning known as induction, or inductive reasoning (figure 3), that works very differently than the hypothetico-deductive method; in fact, quite the opposite. Whereas in hypothetico-deductive reasoning, you start with an idea and use nature to confirm your idea. In generalization, you start with something in nature, you assume it behaves similar to other things like it, then you classify it with those other similar things or ideas. You can also use generalization to make predictions about how things will behave if you know their classification. For example, if you find a new animal species that has hair and mammary glands, you can classify it as mammal. Since it's a mammal, you can predict that it will give birth to live young (if it's female) and is warm-blooded. Generalizing, however doesn't mean you will always be correct; just correct most of the time. We can, for example, generalize that mammals have teeth and birds have beaks, but if we find a duck-billed platypus, a strange Australian creature with a duck-like beak, you would be wrong to assume it's a bird. It's actually a mammal. Further investigations would reveal that it a mammal that retained many primitive features in it's evolutionary development.
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| Duck-billed Platypus |
Synthesis
Biological classification is a perfect example of how generalization is liberally employed in the study of nature. We generalize about other areas of nature as well: chemicals and materials, diseases, stars and planets, subatomic particles, etc. Like the hypothetico-deductive method, it's also a central role in our understanding of nature. A generalization is kind of like a researched hypothesis. Both are used to build more knowledge from data. and the two flowcharts used above are actually similar. We could, thus, use two flowcharts (figure 4) that describe the two processes and, like Francis Crick did to molecular biology, call the charts the central dogma of science.![]() |
| Figure 4: The Central Dogma of Science |
It is also quite convenient that the two methods are very similar. The steps are essentially identical, except we are basically going in opposite directions. In hypothetico-deductive reasoning, we use an idea to predict a behave in nature. In generalizations, we observe behaviors in nature to generalize about an idea (many of types of creatures behave similar enough to create categories like mammals, birds, etc.). The flow of information is also cyclical in both cases. The results of a experiment creates more knowledge and the knowledge created by generalization allows us to predict the appearance and/or behavior of nature. We can conceptually combine the two process to create a more streamlined central dogma(figure 5).
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| Figure 5: Stream-lined Central Dogma of Science |
What Lowly Artisans Taught Elite Philosophers
Episteme was an ancient Greek word that roughly translates to knowledge. Episteme, however, wasn't any kind of knowledge, but rather a specific type of reliable, accurate knowledge that comes from logical contemplation or logos. Another type of knowledge was what the Greeks called Gnosis. This type of knowledge came from experience or emotion; from 'the gut'. It's generally considered to be less reliable but not necessarily wrong. Note also that episteme can be wrong as well, as when your logic is faulty. Aristotle for example 'reasoned' that the earth was the center of the universe, a vacuum cannot exist, men were more intelligent then women, and Greeks were the smartest people in the world, among numerous other errors.One of the major reason Aristotle and other Greek philosophers were often wrong is because they distrusted nature. Philosophical contemplation, for the Greeks, was a mental and spiritual activity. It connected humans with the perfect, quintessential, and spiritual elements of heaven; the imperfect world of nature corrupted this purification ritual. Luckily though, not everyone reasoned the 'proper' way. Paramedies and Plato advocated this extremest perspective of logic and reason, but most everyone else found it quite difficult to learn anything new if you could not look to nature.
Aristotle himself had a falling out with the Platonic orthodoxy by claim some observation of nature was necessary. Another group of people who relayed heavily on nature for new knowledge was a thriving community of medical professionals, or people we now-a-days call doctors or physicians. Unlike modern-day physicians, physicians of the ancient world were not formally trained in medical schools. They were more like craftsmen, who got their training from apprenticeships. In fact, doctors in the ancient world were in the same social class of lowly artisans. But like modern-day doctors, they conducted extensive research while treating patients. From as early as writing was first invented, doctors were recording case studies and histories, listing diseases and ailments, and even using their reasoning skills to conduct research, long before Aristotle and Francis Bacon articulated the processes.
Sometime in the 2nd century BC after the establishment of the library at Alexandria, there were a group of physicians who were worried about the quality of research and a growing lack of experimental rigor in the medical sciences. The past few centuries had experience a flowering of ideas that accumulated into a body of knowledge known as the Hippocratic corpus, much of which, but not all, was written by the semi-legendary Hippocrates. This was a great thing for scientific progress, mind you, but sometimes admiration for greatness and great people morphs in to a sort of hero worship, where the heroes and their works are blindly followed as unquestionable authority. Platonic ideas about heavenly perfection were making their way in the medical sciences as well. A system had been taken shape in which health was viewed as balance of 'humors' and restoration of health was achieved by restoring the balance. Doctors began to relay less and less on physical and natural observation and more and more on the system and the word of authority.
The concerned group of physicians became known as the Empiric school, and pushed for more emphasis on things like effective treatment, observation, and basing treatment of those observation rather an abstract reasoning process or authorized sources. The physicians they opposed became known as the Dogmatic school. The word dogma was actually a Greek word that simply meant a doctrine or set of theories.
Some of ideas of Dogmatic school, like the philosophical reasoning process outlined by Aristotle, turned out to be quite useful, but it was the Empiric school that provided the final step: experience, or communication with nature. When Francis Crick used what he thought was a religious word to describe the central doctrine of molecular biology, little did he known that is was a word that comes from ancient medical sciences.
Similar Lessons
- God, Science and the Joy of Pattern Recognition (or Parmenides vs. the Naturalists)
- The Triumph of Naturalism and the Legacy of the Weeping Philosopher
- Greek Colonies in Italy, Early Healthcare, and Guinea Worms
- A Brief History of Hunting: from Wild Animals to Subatomic Particles
Online Resources
Understanding Science: How Science Really Works - University of California Museum of Paleontology
Evaluating Scientific Claims (or, do we have to take a scientist's word for it) - Janet Stemwedel, Scientific American Blogs
How rationality can make your life more awesome -Julia Galef; Rationality Speaking blog
Further Reading
Richard Dawkins. 2011. The Magic of Reality: How We Know What's Really True. Transworld Publishers Limited.
Susan Haack. 2005. Defending Science—Within Reason: Between Science and Cynicism. Prometheus Books.
Edward Theodore Withington. 1894. Medical History from the Earliest Times: a Popular History of the Healing Arts. London: The Scientific Press limited.

















