Saturday, 6 June 2009

How to think straight

Our brains have evolved in such a way that thinking around corners is something we do naturally. We are by nature problem solvers and we are always trying to spot the patterns in the world around us - in fact we are happier with a pattern than without one even if we have to make it up because no such pattern exists. We can fall into the trap of making false arguments which don’t make sense - we will literally think around corners sometimes.

“Logical errors are, I think, of greater practical importance than many people believe; they enable their perpetrators to hold the comfortable opinion on every subject in turn.”
Source: Bertrand Russell
“There's a mighty big difference between good, sound reasons and reasons that sound good.”
Source: Burton Hillis

Here are a few examples of thinking round corners, how to spot them and hopefully how to straighten out your own thought processes a little.

Please keep in mind that throughout this piece I am talking about thoughts and arguments relating to factual claims, not subjective feelings or value judgements. You may prefer Mozart to Beethoven, but no matter how straight you think and talk you can’t prove you are right or wrong. It is therefore very helpful in life to be able to identify when we are thinking and talking about facts and logic as opposed to aesthetic opinion or a moral choice. Such a thought is a way of coming to a conclusion or making a case or outlining an argument.

Structure of a Logical Argument.

Whether we are consciously aware of it or not, thoughts of this type all follow a certain basic structure.

Premise 1: If A = B,

Premise 2: and B = C

Logical connection: Then (apply principle of equivalence)

Conclusion: A = C - This is my idea of thinking straight.

In order for a conclusion to be considered valid all the premises of an argument must be true, and the logical connection must be valid.

By “valid” we specifically refer to such conclusions, because a conclusion may still be “true” even if it is not valid. This is because it is possible to use wrong information, or faulty logic to reach a conclusion that happens to be true. You can do the math wrong but still get the right answer sometimes. An invalid argument does not necessarily prove the conclusion false. Demonstrating that an argument is not valid, however, removes it as support for the truth of the conclusion.

A key skill for thinking straight is therefore being able to correctly identify the components of the argument. This enables us to examine both our own arguments and those of others and critically analyse them for validity. This is an excellent way of sharpening one’s thinking, avoiding biases, and making effective arguments.

Examine your Premises

As stated above, in order for an argument to be valid all of its premises must be true. Often, different people come to different conclusions because they are starting with different premises. So examining all the premises of each argument is a good place to start.

There are three types of potential problems with premises. The first, and most obvious, is that a premise can be wrong. If one argues, for example, that evolutionary theory is false because there are no transitional fossils, that argument is invalid because the premise – no transitional fossils – is false. In fact there are actually tons (in every sense of the word) of transitional fossils.

A second type of premise error occurs when one or more premise is an unwarranted assumption. The premise may or may not be true, but it has not been established sufficiently to serve as a premise for an argument. Identifying all the assumptions upon which an argument is dependent is often the most critical step in analysing an argument. Frequently, different conclusions are arrived at because of differing assumptions.

Often people will choose the assumptions that best fit the conclusion they prefer. In fact, psychological experiments show that most people start with conclusions they desire, then reverse engineer arguments to support them – a process called rationalisation.

One way to resolve the problem of using assumptions as premises is to carefully identify and disclose those assumptions up front. Such arguments are often called “hypothetical,” or prefaced with the statement “Let’s assume for the sake of argument.” Also, if two people examine their arguments and realise they are using different assumptions as premises, then at least they can “agree to disagree.” They will realise that their disagreement cannot be resolved until more information is available to clarify which assumptions are more likely to be correct.

The third type of premise difficulty is the most insidious: the hidden premise. Obviously, if a disagreement is based upon a hidden premise, then the disagreement will be irresolvable. So when coming to an impasse in resolving differences, it is a good idea to go back and see if there are any implied premises that have not been addressed.

Let’s go back to the transitional fossil example again. Why is it that scientists believe we have many transitional fossils and evolution deniers (creationists or intelligent design proponents) believe that we do not? This would seem to be a straightforward factual claim easily resolvable by checking the evidence. Sometimes evolution deniers are simply ignorant of the evidence or are being intellectually dishonest. However, the more sophisticated are fully aware of the fossil evidence and use a hidden premise to deny the existence of transitional fossils.

When a palaeontologist speaks of “transitional” fossils, they are referring to species that occupy a space morphologically between two known species. This may be a common ancestor, in which case the transitional fossil will be more ancient than both descendent species; or it can be temporally between two species, the descendent of one and the ancestor of the other. But in reality we often do not know if the transitional species is an actual ancestor or just closely related to the true ancestor. Because evolution is a bushy process, and not linear, most of the specimens we find will lie on an evolutionary side branch. But if they fill a morphological gap in known species, they provide evidence of an evolutionary connection, and therefore qualify as transitional.

For example,
archaeopteryx may not be on the direct path to modern birds, but clearly they occupy a space that is transitional between therapod dinosaurs and modern birds and one of their close relatives is a direct ancestor to modern birds.

When evolution deniers say there are no transitional fossils their unstated major premise is that they are employing a different definition of transitional than is generally accepted in the scientific community. They typically define transitional as some impossible monster with half-formed and useless structures. Or, they may define transitional as only those fossils for which there is independent proof of being a true ancestor, rather than simply closely related to a direct ancestor – an impossible standard.

The next post will discuss logical fallacies.

Original article by Steven Novella, MD, (

Posted by the New England Skeptical Society, 5/8/2006 (

Edited and updated by Psiloiordinary, 2006 - with kind permission from Dr. Novella

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