Another reason we need the Bible...

“Without the Bible’s revelation of the majesty and holiness of God, man has no conception of the glory from which he has fallen, or of his present predicament. His need is for a reconciliation that will change both his status and nature as a sinner. It is a need that cannot be met without divine action. When Christianity ceases to be God-centered, a superficial understanding of sin will always follow; sin is treated as a mere unhappiness of dissatisfaction instead of rebellion against God. Consequently the wrath of God passes out of sight, and with it, the necessity of the substitutionary death of Christ. Men reject the penal sufferings of Christ ‘because they do not see the problem’.

"In the same way, low views of God and light views of sin bring superficial ideas of what is involved in regeneration, when sinners are brought from death to life and created anew in the image of God. God alone can achieve such a change: ‘With men it is impossible, but not with God’ (Mark 10:27). All is ‘to the praise of the glory of his grace’ (Eph. 1:6). ‘For of him, and through him, and to him, are all things: to whom be glory for ever. Amen’ (Rom. 11:36)."

– Dr. Martyn Lloyd-Jones, Lloyd-Jones – Messenger of Grace (Edinburgh: Banner of Truth, 2008), p. 8.