Grammar lesson on Faith

The tenses of the verb "pisteuo" (greek word "faith") are also instructive.  The aorist tense points to a single act in past time and indicates the determinative characteristic of faith.  When a man comes to believe he commits himself decisively to Christ.  The present tense has the idea of continuity.  Faith is not a passing phase.  It is a continuing attitude.  The perfect tense combines both ideas.  It speaks of a present faith which is continuous with a past act of belief.      --Leon Morris, New Bible Dictionary