Lack of imagination

An argument by lack of imagination is the logical fallacy that states because something is currently inexplicable, that it did not happen, or that because one cannot conceive of something, it cannot exist. It is used often to attempt to invalidate a scientific theory by pointing out a phenomenon which the theory does not readily explain. This is rather simple to do because there are a lot of phenomena that are currently unexplained. However, the mistake is to assert that because a phenomenon is unexplained, it is unexplainable.

This logical fallacy should be distinguised from the logically valid method of reductio ad absurdum. In reductio ad absurdum it is necessary to show that A implies not A, not merely that A implies something which the speaker considers absurd.

Another example of this argument is Ayn Rand's defense of patent and copyright law. She argued that such laws were "obviously necessary" for authors and inventors to earn a living (or in other words, that she could not imagine any ways for them to earn a living without them, so such methods can't exist), so they should be supported. Rand's conclusion is falsified by, for example, the fact that a wealthy patron (such as a manufacturer creating an advertisement) could commission a work, or that an author could control the work through licensing agreements based on trade secret law rather than through a copyright.

Richard Dawkins has called this fallacy "the argument from personal incredulity"; he uses it specifically in the context of arguments about creationism versus evolution, where it is often phrased in terms such as: "A mechanism that works so perfectly (for instance, the eye) could not have evolved by chance". In a more colorful example he counters a Bishop's implicit assumption that since polar bears are camouflaged even though they have no natural predators, their camouflage serves no evolutionary purpose--the polar bear benefits from the camouflage when hunting of course.

An argument from lack of imagination is arguably part of the teleological argument for the existence of God.