What are Logical Fallacies of Insufficient Evidence?

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  • Written By: Mary Elizabeth
  • Edited By: Niki Foster
  • Last Modified Date: 12 October 2019
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Logical fallacies are errors of reason that can occur in inductive reasoning. Since inductive reasoning moves from the particular to the general, it is important to determine how much and what kind of evidence you need to make a valid argument. Failure to have proper evidence is linked to several kinds of logical fallacies.

Since logic is one of the main techniques used in persuasion, being able to identify and discount logical fallacies in others' arguments and avoid making them in one's own arguments are both important. One of the things that can undermine logic is basing an argument on insufficient evidence. There are several errors that one can make related to insufficient evidence as one chooses evidence to bolster an argument, and the following fallacies of insufficient evidence occur so frequently that they are named.

Hasty Generalization. A hasty generalization bases a conclusion on too little evidence. An example is: This winter was colder than last winter: the climate must be getting colder. This is a logical fallacy of insufficient evidence because more evidence than a change for one year is needed to establish a climatic trend.


Fallacy of Exclusion. Leaving out evidence that would lead to a different conclusion is called the fallacy of exclusion. An example is: In the presidential elections of 2000 and 2005, Florida went to Bush, so it must be a Republican state. In fact, the evidence from 1996, which I purposely excluded from the sentence above, shows that Florida went to Clinton in that election, making this, too, a fallacy of insufficient evidence. By choosing to begin with the data from 2000, I was able to exclude evidence that contradicted the conclusion I wished to draw for the sake of this exercise.

Fallacy of Oversimplification. In this fallacy, some aspects of an issue -- generally more subtle ones -- and their ramifications are not explored. An example is: The question of funding medical research comes down to this: do we want to heal the sick and help the injured to recover -- or not? This argument ignores questions of funding sources, differing states of research in different areas of health care, an so on, so it falls into the category of insufficient evidence. By avoiding reference to any complexities, including the possibility that some issues may never have a successful resolution, this argument makes the choice seem to be solely about good will towards the less fortunate.


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Post 4

@sunnySkys - I think you're right. I often hear logical fallacies in arguments that make sense until you think them through a little more.

I think a lot of people make hasty generalizations regarding either gender. For example, I hear a lot of "My husband never helps out around the house." Then if there are other ladies within ear shot some says something like "Men never do" or "Men are always so lazy." Of course this isn't the case with all men, but the presented evidence makes it seem to be so!

Post 3

I think a lot of groups with extreme viewpoints often lack evidence for some of the assertions they make. And I mean that for groups on the far right or on the far left.

That is why us every day, normal folks need to pay close attention to important issues. We need to actually get the facts in order to form a valid opinion. I think one of the biggest problems with these logical fallacies is that sometimes they actually sound like they make sense! But upon further examination you realize there is insufficient evidence to back it up.

Post 2

It seems to me that hasty generalization is a common way for people to make their point in everyday conversations. There are not many people that would pull out a climate chart to prove you wrong if you say that you think that winters are getting colder and it must be a sign of climate change.

Although you would be lacking a way to prove your point because of insufficient evidence, much of everyday conversation is, and always will be, hasty generalizations. Even our news coverage tends to learn towards sweeping statements, which is where I think the real problem rests.

You would hope that things like news agencies would be more prone to fact checking and making sure they had sufficient evidence, but time and time again you see retractions because they were too hasty because of the need to get a story out.

Post 1

It seems to me that politicians live to use fallacies of oversimplification to get their agendas heard and to sway voters to their sides. While I can understand that it is difficult to get everyone on the same page of a complex issue, it seems to me that the dumbing down of issues is being used more as a tool than as a genuine way to try and help people understand what is happening.

I think you see fallacies of oversimplification happen most often when campaigns deal with things like housing, schooling and funding for things in the community. It seems like it is so much easier to judge a politician's worthiness when you put things like their goals in black and white terms, rather than try and explain why it is we can't have everything we want and how the system works.

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