Allegorical interpretation is assigning a higher interpretation instead of a literal interpretation to the Scripture record of things, in particular to Old Testament stories[1] such as the creation account in Genesis. However, allegorical interpretation leads to problems that a straightforward literal reading of the Bible avoids. For example, given the genealogies that go back to Adam, at some point an allegorical character would have somehow had to "beget" a flesh-and-blood human being. Also, since the soteriology of the Epistles presupposes a literal Adam and compares and contrasts him with Christ, rejection of a literal Adam leads to a rejection of Christianity.
See sensus plenior.