The argument that "all birds can fly" because no bird has ever been seen that cannot fly illustrates what type of fallacy?

The argument claiming that "all birds can fly" based on the lack of observed evidence of any bird that cannot fly demonstrates the fallacy known as an Appeal to Ignorance. This logical fallacy occurs when a conclusion is drawn based solely on the absence of evidence rather than on positive evidence or logical reasoning.

In this case, the argument relies on the idea that since no bird has been observed that cannot fly, it must be true that all birds are capable of flight. This reasoning is flawed because it ignores the possibility that there may be birds that do not fly, but have simply not been observed yet. The conclusion does not follow logically from the evidence presented, highlighting the error in assuming that a lack of counterexamples equates to the validity of a universal claim.

This distinction clarifies why the option is properly identified as an Appeal to Ignorance, illustrating how insufficient evidence can lead to misleading assertions about a wide-ranging group, in this case, birds.