Friday 10 February 2017

Hypotheses, Experiments, Theories and Laws.

One problem debating science with creationists is that the latter are, almost by definition, scientifically illiterate, unless they are defrauding scientifically illiterate creationists for money by misleading them about the science.

So many debates, even those rare ones where the creationist is interested in learning, founder on some basic misunderstanding and confusion of terms. I'm even engaged with one at the moment who is either feigning scientific ignorance or is genuinely ignorant to the extent that he doesn't understand the difference between a definition, a hypothesis and a theory. I'll not bother to define 'definition' (which should be self-evident anyway) but the following is an attempt to define the terms 'hypothesis', 'experiment', 'theory' and 'law' as they apply to formal science.

Part of the problem is that science uses a slightly different but more precise meanings of ‘hypothesis’ and ‘theory’ to that used in vernacular speech. In the vernacular, hypothesis and theory are pretty much interchangeable. Neither has a very definite meaning and sometimes they mean the same as a guess or a hunch, or just a vague feeling. Frequently in vernacular speech, ‘theory’ or ‘hypothesis’ means ‘this is what I would like it to be’ as people often try to fit their idea of reality into a consistent view of the world. Many creationists seem unable to resist the temptation to feign ignorance of this difference or to divert a debate into one about which is the correct meaning.


In science, a hypothesis is a suggested explanation for a phenomenon which is different to the current scientific theory, if there is one. A hypothesis also needs to be falsifiable in that there must be some theoretical way to disprove it. A hypothesis is never formally proven; it is only ever not falsified.

Given that science always proceeds by acknowledging that its theories can be overturned and replaced with better ones, it is only necessary for a hypothesis to be repeatedly shown to be unfalsified for it to be provisionally accepted as the current best explanation. Normally, this would be by at least two independent researchers repeating the experiment exactly and getting close to the same results.

Experiments are designed to test the hypothesis exactly as stated, to check that predictions made by the hypothesis are correct. For this to be done, experiments must eliminate any personal bias from interpretation of the results and eliminate any false positives from the experimental method itself. All experiments are designed to test the 'null hypothesis'. The null hypothesis is a basic assumption in all experiments that the result of the experiment will not be significantly different to there being no effect. No experiment ever proves the hypothesis; the best it can do is to falsify the null hypothesis, in other words show that there was a difference.

Another version of the null hypothesis says that the result of the experiment is purely due to experimental error, bias, and/or personal prejudice, even subconsciously, or something in the method itself that produces the result. For an experiment to be regarded as a success the null hypothesis must be falsified. For this reason, results are often presented in terms of a probability of being false! A result for a biological experiment where there is inherently more variability in the population than in, say, atoms of a given element, a probability of less than 0.05 is regarded as significant. This says that if we repeated this experiment exactly a thousand times, we would expect to get five false results and nine hundred and ninety-five true results on average.

Of course, you can never be certain with any single biological experiment that it is not one of the five in one thousand false ones. To ensure greater confidence, not only should you be able to repeat your results but another team somewhere else should be able to get the same results using your method. Only then does science have any real confidence in the results of research.

If you have been following the Higgs Boson story closely you may remember the CERN team expressed their confidence in the result as ‘at the 5 sigma level’. This is another way of saying they were 99.99965% certain they had found the Higgs Boson; in other words there was a 3.5 in 1 million possibility of being wrong. Note: there was no declaration of certainty. It does not matter how often that test is performed, the possibility of it being another false positive result will never become zero. It will approach it so closely as to make it almost indistinguishable from zero, but it will never become zero (impossible to be wrong).

For everyday purposes though, and certainly with enough confidence to move on to the next steps in physics that this discovery has opened up, the Higgs Boson has been shown to exist (or proven, in the vernacular though non-scientific, sense).

A hypothesis then is an educated guess which seems to explain the observed phenomenon which can be used to make a prediction, and so can be experimentally falsified.


A theory is something else entirely in science. A theory, such as the Theory of Gravity, the Big Bang Theory, the Theory of Evolution, the Quantum Theory or Einstein’s General Theory of Relativity, are not hypotheses. Theories are the widely accepted explanations for a phenomenon, including the entire body of supporting science in the form of observations, experimental results and variations within the interpretations of the evidence.

To quote from Wikipedia:
A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. As with most (if not all) forms of scientific knowledge, scientific theories are inductive in nature and aim for predictive power and explanatory capability.

The strength of a scientific theory is related to the diversity of phenomena it can explain, and to its elegance and simplicity. See Occam's razor. As additional scientific evidence is gathered, a scientific theory may be rejected or modified if it does not fit the new empirical findings; in such circumstances, a more accurate theory is then desired. In certain cases, the less-accurate unmodified scientific theory can still be treated as a theory if it is useful (due to its sheer simplicity) as an approximation under specific conditions (e.g., Newton's laws of motion as an approximation to special relativity at velocities which are small relative to the speed of light).

Scientific theories are usually testable and make falsifiable predictions. They describe the causal elements responsible for a particular natural phenomenon, and are used to explain and predict aspects of the physical universe or specific areas of inquiry (e.g., electricity, chemistry, astronomy). Scientists use theories as a foundation to gain further scientific knowledge, as well as to accomplish goals such as inventing technology or curing disease. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge. This is significantly different from the common usage of the word "theory", which implies that something is a conjecture, hypothesis, or guess (i.e., unsubstantiated and speculative).

So when you see, as you regularly will, a creationist stating as a matter of fact, that ‘Evolution is just a theory’, often followed with ‘- just a guess with no supporting evidence’, you can be as certain as it is that the Higgs Boson has been found that they are either ignorant of the science or lying. In the case of professional creationists who write books and maintain disinformation websites for creationists, you can be certain they have had this error pointed out countless times. They cannot possibly be unaware that their statement is false and a deliberate misrepresentation of science intended to deceive their readers.

It seems to be a characteristic of professional creationists that having a claim shown to be false, is not considered a reason not to try to dupe someone else with it. This basic intellectual and moral dishonesty almost seems to define creationists as much as it does professional religious apologists who do not seem to see having an argument refuted any number of times as a reason not to continue to use it.

I will illustrate what a scientific theory is with a theory that is close to my love of science and in particular biology – the Theory of Evolution. The Theory of Evolution (TOE) is the body of science that seems to excite and distress religious fundamentalists the most.

Many fundamentalist creationists seem to assume that the entire TOE is contained in Charles Darwin’s ‘Origin of Species’ rather like a Christian assumes the whole of Christianity is contained in the Bible or a Muslim assumes the whole of Islam is contained in the Qur’an. In fact, about the only reason to read Darwin’s ‘Origin’ now is as a historical work and to enjoy the brilliance of the mind behind it. It has almost no value as a definitive textbook or reference work.

Like Newton, Darwin was nearly right but also wrong in many respects. Darwin did not know about genes or how information was passed to the next generation, nor did he know about plate tectonics. He believed, as did all his contemporaries, that Earth was very much younger than we now know it to be. He had the same cultural assumptions about racial superiority of Europeans that some people still hold to this day, although he did not translate that into racism in the sense of believing it was alright to treat the ‘lesser races’ as less than human. He was actually an enthusiastic supporter of the abolition of the slave trade and notoriously (if that’s the right word) kind and considerate to his servants.

The modern TOE has its historical origins in Darwin’s and Wallace’s theory of evolution by natural selection, but now incorporates genetics and especially the structure of DNA, comparative anatomy and physiology, fossil records, cladistics, immunology, and even plate tectonics and cosmology. It is a tribute to the robustness of the theory that not a single major scientific advance has ever dented the basic principle of TOE but instead has strengthened it, as we see how well it meshes with other scientific disciplines.

I would go so far as the say that if a scientific discovery appears to contradict evolution, it is vastly more likely that the understanding of the scientific discovery is wrong than that evolution is wrong. What creationists seem unable to grasp is that, so strongly supported is the TOE by diverse strands of science, that when they tell us their religion disagrees with it, they might as well be telling us their religion is wrong. In fact, without realising it that is exactly what they are telling us.

The TOE has now been extended to non-biological systems. Wherever there is imperfect replication and selection, there will be evolutionary change. This change will inevitably be towards better fitness for whatever the selective environment is favouring. The direction of evolution will always be in the direction of greater fitness to produce more copies in that environment. The genetic algorithm is an accepted method for designing complex systems and developing new approaches to engineering problems as in, for example an aircraft wing where there must be an optimal balance between lift, drag, manoeuvrability and fuel consumption at different speeds, altitudes, meteorological conditions and payloads.

We can even make a plausible case for gods, religions, cultures, holy books and science itself being the product of an evolutionary process.

The TOE is no longer seriously questioned by mainstream biologists other than those with a book to sell or a particular extremist religious or political agenda to pursue. It sets the backdrop for all biological research, for a great deal of modern medicine, for embryology and for bio-engineering (whatever you might think of it) and taxonomy. Comparative anatomy and physiology simply would not make sense without the TOE.

Of course there are disagreements, and rightly so, between for example those who think that selection operates more strongly at the group level, the individual level or at the levels of individual genes. These are not necessarily mutually exclusive, incidentally. There were also arguments in the past about whether there was some other factor operating to give ‘punctuated equilibrium’ (PE) or whether natural selection accounted for all the fossil records, including apparently quite rapid changes over a short geological time-span. Some twenty years ago this debate raged between the American proponents of PE, the inspirational author, Stephen J Gould, and the proponent of Darwinian gradualism, the equally inspirational author Richard Dawkins.

Such is the stuff of science. So long as it stimulates debate, tests ideas and interests the audience, long may it continue as a side show. Never in doubt in this debate, however, was the fact that species have evolved from a common ancestor by an entirely natural process. The debate was only ever about the precise details.

The probable reason for the antipathy for evolutionary biology, especially amongst fundamentalist Christians and Muslims is because it goes to the heart of their beliefs about their relationship with their imaginary god. Both religions require the faithful to believe they are the special creation of an assumed creator of the Universe and were somehow created apart from all the other animals.

The fact that Christianity requires its followers to believe they were either, created from dirt (men) or from a rib cutting taken from a man (really?!) and in the case of Islam that they were both created out of mud, requires them to reject that they actually evolved in Africa from an ancestor in common with the other African apes. They are also both required to believe that somehow they are unworthy creations and need to constantly praise their assumed creator and beg its forgiveness. They also have to believe they have a magic being or ‘soul’ living inside them which will be made to suffer hideously after they are dead unless they do so.

The reality is, however, that humans have been evolving by a natural process ever since they diverged from the other African apes and we are only beginning to discover the details of this fascinating story. We are in no sense an unworthy product of a fallen clod of earth; we are an ascended, evolved ape and the product of millions of generations of survivors. We have everything to be proud of and nothing to be ashamed of. It takes the callous psychopathy of the playground bully to tell a child otherwise.

Scientific Laws.

What then is a scientific Law and why are theories not scientific Laws?

In science, the term Law is rather obsolete and tended to be used for early, fundamental discoveries that were universally true, or true within clearly defined conditions. They normally deal with specific, discrete cause and effect situations.

It would probably be possible to formulate it as a Law of Evolution that the frequency of beneficial alleles, in a population subject to imperfect replication of those alleles in a selective environment, will tend to increase. However that really only states the obvious and has little use outside a theoretical discussion of the mechanism of evolutionary change in a biological system.

More useful are those Laws which allow us to make accurate predictions, for example, The Law of Constant Composition (also called the Law of Definite Proportions) and the Law of Multiple Proportions which form the basis of analytical chemistry.

Some Laws, such as Hook’s Law of Elasticity only holds over a certain range. A rubber band will obey Hook’s Law up to a point, but, beyond that point Hook’s Law will fail and there will be a point at which the rubber band will snap.

Perhaps the most famous example of a scientific Law is that derived from Einstein’s Theory of Special Relativity, e = mc2, where energy (e), mass (m) and the velocity of light in a vacuum (c) are in a constant relationship. A given mass of matter will always give the same amount of energy because the velocity of light in a vacuum is a universal constant.

To summarise then, in science:
  • Laws express causal relationships which are either universally true or true within a known range of conditions.
  • Theories are the accepted best explanations for observable phenomena together with the body of confirmatory experiments, evidence and fundamental Laws where appropriate.
  • Hypotheses are the ideas which are tested and either falsified, or confirmed to a high degree of confidence through repeated testing and failure to falsify.

None of these are cast in tablets of stone because probably the only certainty in science is that there are no certainties. Laws are unlikely to be changed but can be if new information shows them to be inadequate. For example, the Law of Conservation of Mass had to be replaced with the Law of Conservation of Energy in view of Einstein’s Relativity. Theories can be overthrown and will almost certainly be modified and will evolve in the light of new information; and hypotheses are made to be destroyed and will be abandoned or reformulated as necessary.

The last point to be made here is the distinction between a scientific Law and a judicial law which are often, probably deliberately, confused in the minds of non-scientific people. This confusion is often used to mislead creationists by telling them that laws need a lawmaker, as though the existence of scientific laws formulated by human beings are evidence of a magic lawmaker somewhere. The confusion here is that a scientific law is descriptive; it tells us what will happen in a given situation. Matter has no choice in the outcome so does not need to understand that it must obey the law or there will be consequences.

Drop a stone and it has no choice but to fall to the ground. This is a Law because it will always happen if you are standing on a planet with gravity. It is a fundamental law of mathematics that 1 + 1 = 2. There is no law that makes one pebble and another pebble make two pebbles. 1 + 1 = 2 simply describes the situation of one pebble next to another and expresses it as a useful model.

Judicial laws however are proscriptive or prescriptive. They are man-made rules that tell you what you can and cannot do or what you must or must not do and what the penalties are for non-compliance. They do not describe what people will always do in a given situation. We would not need judicial laws if people had no choices but we could then express their behaviour with scientific Laws.

The above based on part of Chapter 6 "Knowledge, Science and Uncertainty" of my book, Ten Reasons To Lose Faith: And Why You Are Better Off Without It

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1 comment :

  1. Hear, hear. Well said and elegantly proposed. Sadly, I think you are preaching to the converted on this one. Ain't that the sad truth......


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