David Gross suggests that the idea is inherently unscientific, unfalsifiable or premature. It has been criticized for allegedly being unfalsifiable and for making contradictory predictions. Julia Serano criticizes this conclusion as unfalsifiable. The objection that evolution is unfalsifiable has been widely rejected by the scientific community. A closed-circle argument is one that is unfalsifiable. Indeed, "All men are mortal" is a classical example of an unfalsifiable statement.