The physical mind is limited in its abilities – it simply is not equipped to grasp things of deep spiritual nature. We read in TGRABJ/2/200, “You cannot perceive spiritual things with the material mind, neither can a man by reason of those powers of the mind which know only material things, be able to perceive the truths of the spirit. Hence the necessity for man cultivating the soul perceptions, which are greater and more comprehending than all the faculties of the material mind.”
The Bible concurs and puts it in these words:
1 Corinthians 2:12-14 – We have not received the spirit of the world but the Spirit who is from God, that we may understand what God has freely given us. This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, expressing spiritual truths in spiritual words. The man without the Spirit does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritually discerned.
This chapter discusses the difference between the natural mind and the soul mind in terms of receiving understanding.