A Dangerous Lack of Connection Between Forms of Truth

Gemara: It was said in the name of Rav: The Rabbis attempted to hide the book of Kohelet, because its words contradict each other.

Ein Ayah: The word of Hashem will always prevail. All matters that bring improvements to the world that emanate from divine sanctity must act both according to the low level of the present and the higher level of the future, and these elements should be connected in some way. The Torah, like Hashem’s Name, accomplishes this by having concealed and open elements that are connected. Books of the Torah deal with timeless esoteric matters and also give practical instruction on ethical matters specific to the present condition. These books never need to be hidden because they always give life to those who delve into them.
However, it is dangerous for a book to, on the one hand, contain deep and lofty messages, but, on the other hand, be unable to improve lives in the present because the author addresses matters that people of his time are unable to apply. Such a book needs to be hidden until a time when people will be on the level to be positively impacted by it. That is why the Rabbis attempted to hide Kohelet.
The foundation of belief is that the world exists with its physicality and spirituality. We believe in Hashem’s unity, from which stems the unity of His actions and of His wisdom which unite all disciplines in the world, which share a source and a goal. We trust in the truth of the ideas that were passed to us in purity by means of the Torah, prophecy, divine spirit, and the traditions of holy people. All G-d-fearers should know that truth and eternal light are constants. They must reject those who cast doubts about these holy words in the hearts of the vulnerable and rob them of their spiritual strength.
Therefore, it is very dangerous for there to be apparent contradictions in a book of Tanach, even if, in truth, the contradictions are not internal but stem from their dealing with matters that are so deep that they point outwardly in different directions. Still, the appearance of contradiction to the generation is severe enough. The power that connects the present and the future through these divine ideas are still not strong enough, and present generations can be negatively impacted if they cannot reconcile the contradictions on an external level. If answers to reconcile the contradictions existed, then even if upon going deeper they would not stand, still upon going deeper, new powers to unify the truth would emerge.
Thus, at the time that the Rabbis did not know how to reconcile the contradictions and unite the future with the present, Kohelet was not fit to be an open book for public consumption. It was then liable to pollute and weaken the people’s beliefs. It is critical to view Hashem as "I am Hashem, I have not changed" (Malachi 3:6). We should know that the earliest stages of development, like the pregnancy that precedes the birth and certainly precedes childhood, adolescence and old-age, must be connected to the most complete later stage. There must always be unity and true, internal peace. This is as we say in our prayers, "All believe that He creates them in the abdomen; He is all-powerful and includes all together."