The world around us behaves for the most part in a consistent manner. The sun rises in the morning, objects obey laws of motion, chemicals react according to known formula. However, there are no absolute certainties. What we take to be true sometimes turns out not to be, or turns out to be only an approximation of the truth, and unexpected things can and sometimes do happen.

In support of Common Sense, we should apply general rules as though they were absolute, in most circumstances. But we don’t need to believe they are absolute. Always be willing to acknowledge that there may be circumstances under which our general rules may not be applicable, and always be willing to modify what you believe to be true should there be strong evidence pointing you towards doing so.

When you come across evidence that contradicts your everyday and useful explanations of how the world works you should apply a reasonableness test. When you see what you think might be a ghost or an alien or a pixie are you sure about what you’ve seen. We are well able to see things that aren’t there. Are there other explanations for what you’ve seen? Maybe someone trying to trick you. Maybe you have a false memory. Maybe you are just tired.

Some ways in which what we think we see is not what is actually there arise from (1 of 2):

◦ Our senses can be deliberately fooled such as by optical illusions. Magicians are skilled at fooling our senses, and others are also able to do so, sometimes deliberately to deceive.
◦ We only really notice what we are focusing on. Our eyes only fully see what is within a very small cone in front of us. Most of the rest of what we think we see is actually the result of our brains filling in based upon what it assumes to be there. Sometimes it gets it wrong.

Some ways in which what we think we see is not what is actually there arise from (2 of 2):

◦ We are very susceptible to suggestion. If someone questions us about something we’ve seen, our belief about what we saw can be significantly influenced by the implied suggestions in the questioning. There are many instances of false memories being created in this way.
◦ Our memories of what we believe we saw in the past can be false. When witnessing an accident bystanders often give very different accounts of what they claim to have seen.
◦ ‘Believing is Seeing’: we frequently see what we expect to see, particularly when we are only half paying attention.

In addition to misinterpreting or being mistaken about what we see we are also prone to the poor application of logic. We draw conclusions based on what we think we know, but we are prone to what are termed fallacies.

Fallacies refer to the ways seeming logical arguments can be false or incorrect. The following are a few examples (1 of 3):

◦ Fallacies of Composition and Division: What is true of the whole or a group is not necessarily true of the parts or individuals taken separately; and what is true of the separate parts, even of all of them taken separately, is not necessarily true of the whole. Yet it is common in arguments to find people accidentally or purposefully using part of an argument to refer to individuals but their conclusion concerns the group, or vice versa. Examples: the economy is improving therefore everyone is better off; each member of the team is an expert therefore the output from the team will be brilliant.

Fallacies refer to the ways seeming logical arguments can be false or incorrect. The following are a few examples (2 of 3):

◦ The Fallacy of Single Cause is where it is assumed there must be a particular cause to a given outcome rather than accepting there may be a combination of multiple causes, no one on its own which would have brought about the outcome. Example: children are overweight because of junk food restaurants close to schools.

Fallacies refer to the ways seeming logical arguments can be false or incorrect. The following are a few examples (3 of 3):

◦ The Fallacy of the Unexplained is the presumption that because something is unexplained then it is inexplicable. However just because we do not currently have an adequate explanation for a phenomenon does not mean that it therefore defies the laws of nature or requires a paranormal explanation. Example: because we don’t understand all the details of how life came about it must have been created by intelligent design.

Understanding fallacies, being able to avoid them in your own thinking, and being able to recognize them in others, is an important enabler to the effective application of Common Sense. See our page on Fallacies.

Another common cause of people drawing incorrect or misleading inferences from known information is a poor understanding of probability and statistics. Most people have a poor grasp of probability and make poor everyday judgments as a result.

The following are a few of the many misunderstandings or biases that could be avoided with a good understanding of how probabilities and statistics work (1 of 4):

◦ There will be many patterns readily visible in random data. When looking ‘after the event’ at a set of random data we can often see a pattern in it. There are an infinite number of patterns we can envisage, and therefore finding one to match a set of random data after the event it not difficult, and doing so is known as the Pattern Bias. This doesn’t make it real. Only if the pattern enables us to get good predictions in the future might it be one that is useful to us.
◦ Whilst a given low probability event is unlikely to happen, if there are many possible low probability events the likelihood of one of them happening could be high.

The following are a few of the many misunderstandings or biases that could be avoided with a good understanding of how probabilities and statistics work (2 of 4):

◦ If something is likely, its’ none occurrence does not prove it wasn’t.
◦ Many people mistakenly believe probabilities even themselves out in some causal way. That if they have had a sequence of 6 heads in a coin toss, that a tail is then more likely so as to even out the probability to the known 50%. This is mistaken. The next coin toss assuming an unbiased coin remains a 50% likelihood.

The following are a few of the many misunderstandings or biases that could be avoided with a good understanding of how probabilities and statistics work (3 of 4):

◦ People generally fail to understand how a ‘base rate’ impacts a probability. Take the example of a diagnosis for a disease that is described as 99% accurate, in that only 1 in 100 diagnoses will be incorrect. Most people if then diagnosed as having the disease will consider it highly likely that they have it. However if the ‘base rate’ is that only 1 person in 1 million has the disease, this means that if everyone was tested for the disease 10,000 people who didn’t have the disease would be diagnosed as having it. Thus although someone is diagnosed as having the disease, there is in fact still only a 1 in 10,000 chance that they actually have it.
◦ Averages can be misleading. They can easily be skewed by a few extremes.

The following are a few of the many misunderstandings or biases that could be avoided with a good understanding of how probabilities and statistics work (4 of 4):

◦ Statistics are often used to show causation by showing that there is a relationship between two variables. However simply because there is a relationship does not imply one has caused the other. Correlation does not imply causation. They may both be caused by some other factor. Correlation however does suggest there is some relationship albeit possibly indirect which should be explored.
◦ People overestimate probabilities based on the fact that they can bring particular examples to mind, and tend to be much more influenced by information that is readily to hand. This is known as the Availability Bias.