The argument from fallacy, also known as argumentum ad logicam or fallacy fallacy, is a logical fallacy which assumes that because an argument is fallacious then its conclusion must be false.

Perhaps the simplest way to prove to yourself that this is a fallacy is think of an obvious truthhood and try to construct a fallacious argument in favor of it.

For example:

When I let go of this pencil, Angels from Heaven on high will push it downward. Therefore, it will fall to the ground at a rate of 9.80665 meters per second.

Now, even if you could disprove that angels will exert downward pressure on your pencil, it would not follow that if you let go of the pencil then it would not fall to the ground. It just means that "angel theory" is not a sound way of reaching that conclusion, regardless of the conclusion's truth or falsity.

Other Examples:

Anne: "All cats are animals. Ginger is an animal. This means Ginger is a cat.".

Bill: "Ah you just committed the affirming the consequent logical fallacy. Sorry, you are wrong, which means that Ginger is not a cat". (But of course, while it is not certain that Ginger is a cat, Ginger might be one.)

Bill: "OK - I'll prove I'm English - I speak English so that proves it".

Anne: "But Americans speak English too. You have committed the package deal fallacy, speaking English and being English don't always go together. That means you are not English".

Showing that arguments given for a position are fallacies does not disprove the position. It may, nevertheless, be correct; the argument merely should not compel anyone to believe, either way.