- Ad hominem (attacking the arguer instead of the argument)
This is usually done through name calling or labeling the person something deemed negative. This usually happens when a person runs out of reasons to support their argument so have to resort to attacking your character. It is important to understand when this is happening as it can negatively influence decisions. It also speaks to a greater problem of respect in the project team.
- Cherry picking (suppressed evidence, incomplete evidence)
Act of pointing at individual cases or data that seem to confirm a particular position, while ignoring a significant portion of related cases or data that may contradict that position. This problem is more apparent when you have a strong personality doing the cherry picking as others will not speak up to point out suppressed evidence. When you do not feel good about an argument, it is sometimes a good idea to talk individually to each person to hear all the facts.
- Hasty generalization (fallacy of insufficient sample, leaping to a conclusion)
Basing a broad conclusion on a small sample. This hurts when people are too quick to fix something before they understand the real problem or if a problem really exists. A good project change and escalation control structure can reduce this fallacy.
- Argumentum ad baculum (appeal to the stick, appeal to force, appeal to threat)
An argument made through coercion or threats of force to support position. This is something I see between business and their IT or business and a vendor. This can work for short term issues, but it hurts the long term relationship which can bring much more to the table.
- Argumentum ad populum (appeal to belief, appeal to the majority)
Where a proposition is claimed to be true or good solely because many people believe it to be so. This is something I use to start the conversion on an issue. You first want to ask what everyone else does. In saying that, you should never base the final decision on this alone. It should be based on the facts on why the proposition is true as there are cases where it will make more sense for you to go with a different direction.
- Appeal to authority
Where an assertion is deemed true because of the position or authority of the person asserting it. This is another one that can be abused a lot in projects. When an argument is not going their way they start to list all their years of experience in explaining why their decision is correct. If your experience is so great then you should have a lot of great facts on why your point of view is correct.
- Appeal to emotion
Where an argument is made due to the manipulation of emotions, rather than the use of valid reasoning. This one people do as second nature and can be both positive or negative. A good negative example is setting the tone of an argument by making it sound ridiculous from the start. A positive example is first telling the listener how wonderful they are before you make your argument.
- Appeal to motive
Where a premise is dismissed by calling into question the motives of its proposer. This is similar to ad hominem as a person will use this when they have run out of reason to support their argument.
- Appeal to tradition
A conclusion supported solely because it has long been held to be true. There comes a point where the only reason someone does something is because it is the way it has always been done. Tradition can be great, but not when your project has a tight budget and timeline.
- Straw man
An argument based on misrepresentation of an opponent's position. This one can be very subtle where a person will rephrase your proposition to make it harder to defend. An example is asking that all the project managers are given corporate cards and person B responds that if everyone in the company was given cards it would increase spending. In this case, it is much harder to prove the need for giving everyone a card versus only project managers.
Projects inherently involve a lot of communication from a lot of people with a lot of different backgrounds. This type of environment provides a breeding ground for fallacies which results in poor decisions that ultimately hurt the success of the project. Below is a list of ten common fallacies you will see in projects. The list is a subset of what I found in Wikipedia with my thoughts added at the end each definition.