Scripture can be interpreted only by the Holy SpiritTrue understanding is not natural to us; it is God's gift (Mt11:25, 16:17) through the Holy Spirit (Jn. 16:13f.). This neither absolves us from hard work, nor implies that we can isolate ourselves from other Christians in our understanding of the Bible.
This [third] hermeneutical principle carries a profound spiritual challenge. God's Spirit is holy; therefore what we understand of his truth is related less to the capacity of our brains than to the extent of our obedience. How far one can see depends on how high one has climbed rather than on how elaborately one is equipped. 'Blessed are the pure in heart, for they will see God.' (Mt. 5:8)
-- pp. 61-62, Know the Truth by Bruce Milne (italics original)
We need to engage our mind as we read the bible, but the understanding will be given to those who obey God, those with the pure heart.