G. Reale, A History of Ancient Philosophy: The Schools of the Imperial Age, trans. John R. Catan (Albany: State University of New York Press, 1990) 22-23.
The lucidity which the preceding age prized was the assett of the exoteric works of Aristotle; in the centuries of the Roman empire they appeared popular. Then men become passionate about the recondite and the mysterious. Effort is the law of style; ideas more than words are valued as are sentences which carry a hidden meaning. The fascination about the Hermetic doctrines of the East had penetrated the Roman spirit. Obscurity does not frighten, rather it fascinates. If the new religions have mysteries for initiates, why not the religion of truth, philosophy? Also, the God of philosophical thinking does not appear to all but only reveals himself to those who merit it, beyond the internal part, in the innermost recesses of the temple. As Pythagoreanism, which is in fashion, so every philosophy must have secret doctrines and sacred 'orgies' of the mind to which only the initiated are admitted...Such a love for the arcane brought gradually to the esoteric works of Aristotle the attention of the later centuries of the declining Classical Age.
Reale is discussing the popularity of the "esoteric" works of Aristotle, the cryptic ones that have a hidden meaning (I think). For Reale, Aristotle's esoteric works were not all that popular for some time, when philosophers preferred Aristotle's clear writings in their own pursuit of clarity and consistency. Later, however, philosophers became attracted to the cryptic, and Aristotle's esoteric writings made a comeback.
Reale talks about why the "esoteric" is so popular. Many like a mystery, and they enjoy being part of a clique that is "in the know." People have characterized the Armstrong movement as like that.
But is there esotericism in the Bible? Some have argued such. When I was at Jewish Theological Seminary, Jacob Milgrom seemed to contend that God was giving Moses inside-knowledge that the other Israelites did not receive. Exodus 3 presents God telling Moses that God's name is "I will be what I will be," but he instructs Moses to inform Israel that is name is merely "I will be." The Israelites were to learn that God exists, but Moses was given an additional nuance of information about the divine that was hidden from the other Israelites.
I don't quite remember what special information Milgrom thought Moses was receiving, but I do recall that he was associating "I will be what I will be" with Exodus 33:19: "I will be gracious to whom I will be gracious, and will show mercy on whom I will show mercy" (NRSV). Exodus 33-34 is significant because Moses was seeing something of the glory of God, as God proclaimed, "The LORD, the LORD, a God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness, keeping steadfast love for the thousandth generation, forgiving iniquity and transgression and sin, yet by no means clearing the guilty, but visiting the iniquity of the parents upon the children and the children's children, to the third and the fourth generation" (Exodus 34:6-7).
I've heard Christians interpret Psalm 103:7 in light of esotericism. The passage states that God "made known his ways to Moses, his acts to the people of Israel." For such Christians, the Israelites got to see God's outward acts, but Moses was clued in about God's ways: his character, his motives, etc. If I'm not mistaken, that's what they think is going on in Exodus 34:6-7.
Maybe there's something to that. I don't know. It seems to me that God didn't want to keep the children of Israel totally in the dark about his ways, however, since much of God's character described in Exodus 34:6-7 also appears in the Ten Commandments (Exodus 20), which all of Israel presumably knew.
There are clear examples of esotericism in the Bible. For example, Jesus states that he speaks in parables to obscure the truth (Mark 4:11-12). At the same time, I don't think that he wanted the truth to be permanently concealed. After all, we Christians have the Bible, which contains Jesus' decoding of the parables. And Matthew 28 says we are to teach all nations what Jesus taught us, which presumably includes those explanations. So Jesus eventually moved beyond esotericism. In my opinion, God does not forever hide the truth or limit the number of people who know about it, for he wants everyone to hear it.