I’ve noticed that quite often people commit a logical fallacy that isn’t part of the classic list of fallacies.
The Package Deal Fallacy: Inferring (and attacking) from a speaker’s belief in one idea (A) that they must believe another idea (B) that is not a necessary logical result of A but which is frequently associated with it. Belief in A is presumed to constitute a “package deal” including belief in B. A and/or B could also be actions frequently associated with other beliefs or behaviors.
Below are some examples of the fallacy in action with some commentary on each:
1) John is opposed to gun control laws. Therefore, John must also oppose same-sex marriage because opposition to gun control laws is frequently associated with opposition to same-sex marriage.
People frequently make assumptions like this because we are so accustomed to seeing that people who oppose gun control laws also oppose same-sex marriage. It is frequently true that people hold these beliefs in tandem, but there is no logically necessary connection between them.
2) Frank is an avid NASCAR fan, so he must be opposed to gun control laws, because most NASCAR fans are Republicans and most Republicans oppose gun control laws.
Here we have an instance where a behavior is associated with both another behavior and a belief, neither of which are a necessary result of the initial behavior.
3) Jack says that he does not believe that the neo-Darwinian synthesis is true because he does not believe that mutations occur randomly. So he must not believe in common descent and therefore believe in ex-nIhilo creationism.
This example is a bit more subtle, because Jack has expressed disbelief in a position that is itself a package deal composed of many different elements. The key here is recognizing that Jack has criticized only one specific element of the package deal. Here therefore cannot subscribe to the deal as a whole, but that does not commit him to believing that the rest of the theory is in error. Jack may well believe in common descent but he may well disbelieve in the random element of mutations. He may be mistaken in disbelieving in the randomness of mutations, but this does not commit him to disbelief in common descent. I suppose that one could say that this instance of the fallacy is a subspecies of Strawman Argumentation because it misrepresents a speaker’s position.
Why is it that people commit this sort of fallacy? I believe that it is simply because we are conditioned through repeated experience to expect that beliefs or desires that are frequently conjoined are necessarily conjoined. As David Hume put it, “after a repetition of similar instances, the mind is carried by habit, upon the appearance of one event, to expect its usual attendant, and to believe that it will exist.” We thereby infer a necessary connection although no such connection may exist.
I try my best to avoid this kind of sloppy thinking, and I encourage you to do the same.