3) Critical Thinking: Testing which ideas are true

Using your imagination and thinking creatively is a great first step but it is not enough. Ideas are not all equal some will prove to be incorrect. It is important to apply critical thinking to eliminate errors and allow ideas to be tested and their usefulness accessed. The following video introduces critical thinking and its importance.

Critical Thinking

Logical fallacies are important in critical thinking because they are errors in reasoning. Many books have been written about logical fallacies. Typically these books were written by people who were logicians and their primary interest was in the “abstract” world. With this starting point they divided fallacies into two categories: formal fallacies and informal fallacies.

1)    Formal fallacies are errors in deductive reasoning. This is an exercise in consistent deductive reasoning. From a given starting point, premise or axiom the conclusion can be deduced. If the starting point is true the conclusion must also be true. No are no other possibilities. It is an Abstract World exercise only. Physical World arguments are not used in deductive reasoning.

The absolute nature of this Abstract World truth was and remains very appealing. It is one of the foundation of mathematics and people described mathematics as “the language with which God has written the Universe” (Galileo Galilie). Until the rise of science formal logic and mathematics were preeminent. This changed with the success of science. Now logicians had to account for this success. For many science was a process of observation and then inferring a general rule: i.e. Inductive reasoning.

2)    Informal fallacies are classed as errors in inductive reasoning. Inductive reasoning is not absolute. Inductive arguments support their conclusions they do not prove them.

For example:
Every day to date the law of gravity has held. Therefore, the law of gravity will hold tomorrow.
There is no logical proof that the law of gravity will hold tomorrow.

Even a good inductive argument that is logically consistent with a true starting point or premises can lead to a false conclusion. Or put the other way round: a false starting point can lead to a true conclusion. From the point of view of logic there is deductive reasoning which leads to proof and then there is everything else.  The everything else is grouped together and termed inductive reasoning. Formal fallacies result from bad reasoning. However, informal fallacies may not result from bad reasoning so they are usually identified in terms of strong or weak arguments.  I.e. arguments that fail to meet the standards required of inductive arguments commit fallacies in addition to formal fallacies. There is one big problem with this approach which is defining what is the required standard is for an inductive argument. Definitions are not clear and as a result the books written of critical thinking that use this approach are not as useful as they should.

There is no proof in the Physical World. As in the gravity example, however many observations you make does not prove something. However, logic can still help because you can disprove a theory that makes predictions. For example, the theory that all Swans are white can be tested. If you find a single black Swan you can disprove the theory.

Therefore in the world of informal fallacies it possible to identify them in relation to arguments that make predictions that can be tested, in the physical world and disproved. Strong arguments are ones that have better survived testing than others.