"Survival of the fittest" is a tautology (Talk.Origins)
Natural selection, or "survival of the fittest," is tautologous (i.e., uses circular reasoning) because it says that the fittest individuals leave the most offspring, but it defines the fittest individuals as those that leave the most offspring.
Source: 'Gish, Duane T., R. B. Bliss and W. R. Bird. 1981. Summary of scientific evidence for creation. Impact 95-96 (May/Jun). 
Morris, Henry M. 1985. Scientific Creationism. Green Forest, AR: Master Books, p. viii.'
Creationists agree that this argument shouldn't be used to falsify evolution. See Arguments we think creationists should NOT use