In other words, these people believed only for a while; and therefore if their belief was the result of salvation, their salvation did not bring them a lasting faith: this to me appears to be declaring a false doctrine that I recently encountered, that a man can fall away from the faith and will still be saved. It is either that, or the faith that is spoken of in Luke 8:13 was not a saving faith. Or, the person had a saving faith but saving faith does not produce everlasting life.
I have answered this by saying that a nominal, lukewarm, or shallow faith is not a living and saving faith; because it amounts to mere mental assent to the tenets of the gospel. But that a heart faith (Romans 10:10) is unto righteousness (see Matthew 5:6, Romans 5:19, 1 John 3:7) and will endure unto the end also (see Hebrews 3:6, Hebrews 3:14, Matthew 10:22).