The basic fallacy states that X wouldn't have happened if Y hadn't happened. Therefore, Y caused X.
The reason I call it the "if-only" fallacy is because this fallacy usually occurs after some sort of accident or tragedy, when some main character says to himself "IF ONLY I had done something different, this wouldn't have happened." And feels guilty about something that probably wasn't his fault.
- Five year old Laura is sitting in the living room watching television, and a stray bullet from a gun fight outside goes through the front window and hits Laura, instantly killing her.
- The mother feels very guilty and thinks to herself "if only I hadn't let Laura watch television today she wouldn't have gotten killed. Any sort of responsible mother wouldn't have let her daughter watch television! I should have been reading to her, or spending quality time with her! It's all my fault."
The fallacy is the assertion that if the mom hadn't let Laura watch television, Laura wouldn't have gotten shot, and therefore the mom caused Laura to get shot.
Obviously, this isn't true. It was not the mother's fault that the kid got shot. Hypothetically, you could say that the mother was responsible for her kid not being smart enough because of watching television, but you can't logically say that the mother caused or was responsible for the killing. There are plenty of other "if only" statements that could apply to the same situation:
- If only guns hadn't been invented... the invention of guns caused this
- If only they didn't move into that neighborhood... moving there caused this
- If only the mom had taken the daughter to the store instead of doing housework...
- If only the mom had kept her job, and put her daughter in daycare...
- If only Laura had been made to take a nap at that time...
- If only Laura had been allowed to stay with Aunt Mary that day... but nooo Aunt Mary was too "busy"
- If only...
The list could go on forever. Yet when you actually think about who is culpable for the crime, it is obvious that it was one of the people in the gunfight outside who was truly responsible for the death of the little girl.
Another common use of this fallacy is when people try to shift blame to another person for their own actions.
- David yells at Daniel, and Daniel slaps David.
- Daniel then explains to his mom that it wasn't his fault: that if only David hadn't yelled at him, he wouldn't have slapped David. It's David's own fault, then, and not Daniel's fault.
The fallacy is in the assertion that if David hadn't yelled at him, Daniel wouldn't have become violent, and therefore David was the cause of the violence.
Obviously this isn't true. Daniel determines his own actions, whatever may influence him, and is responsible for what he himself determines to choose. In psychology, this is referred to as an "external locus of control." People like that view what controls them as outside of themselves. This type of person is always blaming others for their own bad decisions. On the contrary, people with an "internal locus of control" views themselves as capable to choose how to respond to their environment, and take responsibility for their own actions.
So, to summarize, the "if only" fallacy states that X wouldn't have happened if Y hadn't happened. Therefore, Y caused X.
It is not always true. Most of the time, Y did not cause X, as in the examples above. However, sometimes it is true that Y caused X. For example, if only I hadn't dropped the egg, it wouldn't have broken. Dropping the egg caused the egg to break.
Therefore, saying that "if only" X hadn't happened, Y wouldn't have happened does not prove the point one way or another. I would also say that it's an important fallacy to avoid because, as you can see from the example I gave, it can lead to either false guilt or irresponsibility.
From Get Smart:
*Max throws bomb out of the window, and it lands on Chief's car and explodes*
*Cut to Chief and Max, in Chief's office, discussing the incident*
Max: Thank goodness you're alright, Chief!
Chief: Yes. I would have been in the car, except I stopped to pick up a pack of cigarettes. Do you realize that that pack of cigarettes saved my life?
Max: And they say smoking is bad for you...!