Reports on two types of unsolvability in mathematics. One is an instance of impossibility and the second is a judgment of undecidability. Presents a number of examples of undecidable propositions. (GS)

Reports that a congenitally blind child, as well as sighted but blindfolded children and adults, can determine the appropriate path between two objects after traveling to each of those objects from a third object. Explores relationships of finding to geometric principles underlyinq innate spatial knowledge and inferential ability. (Author/CS)