The following is a favorite argument made by those who would have the masses ignorant of bible truth: The bible is just too complicated to understand. The psychological effect is devastating. After all, if it is too complicated to understand, why try? And most do not.
Bible complexity is an interesting subject. On the one hand, the myth that the bible is too complex to understand was destroyed by the Apostle Paul when he said: "... by revelation he made known unto me the mystery; (as I wrote afore in few words, Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)" (Eph. 3:3-4).
On the other hand the bible is not trivial. The Apostle Peter referring to the writings of Paul stated "in which are some things hard to be understood" (2 Pet. 3:16).
It is not difficult to reconcile these two views. Peter did not say that all things were hard to be understood. We can be safe in concluding that parts of God's word are quite simple (2 Cor. 11:3), while others are much more challenging.
The Apostle Paul (1 Cor. 3:2) and the Hebrew writer (Heb. 5:12) both spoke of the milk of the word which was easily digested, as opposed to the meat, which required more maturity for its discernment.
There is a lesson here for both the weak and the strong. To the babe in Christ: God expects us to render obedience in all things which we understand to be His will (Heb. 5:9). It is our job, not just to believe that He exists but also to "diligently seek him" (Heb. 11:6). Growth is an essential part of the life of the Christian, and this requires the addition of knowledge (2 Pet. 1:5-8).
To those who freely feed upon the meat of God's word, it should be recognized that you never "arrive." Indeed, it was those who had the most knowledge of God's word who were the recipients of the harshest rebuke from our savior (Mt. 23).
The fact that the bible cannot be totally mastered is further evidence that its author was none other than God. The fact that its first principles are so simple adds to this evidence. The bible is the most efficient book ever written guiding us to every possible good work (2 Tim. 3: 16-17) while containing absolutely no useless information (Mt. 4:4).
There is a reason that most people cannot understand God's word, but it has nothing to do with intellectual ability (Mt. 11:25, 13:10-17).