Packer answers the question of whether or not biblical thinking is legitimate or obsurantist? He argues that since the darkened mind is in bondage to sin, true liberty of thought can only occur as our minds are subject to the mind of Christ.

“Do evangelical principles inhibit the freedom of reason? On the contrary, they establish it. Freedom is no merely negative conception; anarchy is not freedom, either on the moral or on the intellectual level. True freedom is something positive: to possess it is to fulfill one’s human destiny. Such freedom is found only in subjection to God and His truth; and the more subject, the more free-this is the biblical paradox of Christian liberty. Man becomes free only in bondservice to Jesus Christ; otherwise, he is captive to sin. Man’s mind becomes free only when its thoughts are brought into captivity to Christ and His Word; till then, it is at the mercy of sinful prejudice and dishonest mental habits within, and of popular opinion, organized propaganda and unquestioned commonplaces without. Tossed about by every wind of intellectual fashion and carried to and fro by cross-currents of reaction, man without God is not free for truth; he is for ever mastered by the things he takes for granted, the victim of a hopeless and everlasting relativism. Only as his thoughts are searched, challenged and corrected by God through His Word may man hope to rise to a way of looking at things which, instead of reflecting merely passing phases of human thought, reflects God’s eternal truth. This is the only road to intellectual freedom, and its sole safeguard is the principle of absolute subjection to Scripture.” (Packer, J. I. Fundamentalism” and the Word of God. Wm. B. Eerdmans Publishing Co., 1958, 143)