Esotericism is contrary to the nature of Christianity.
Most esoteric sects and authors and intellectuals with ties to occultism, in addition to the Rosicrucians and various Masonic Lodges, are convinced that Christianity has “secrets” regarding religious content it does not reveal, as if there were an “esoteric Christianity.”
The truth is that such a thing—a reserve of hidden doctrinal truths that only an elite group knows —never existed in the past, nor does it exist now. That is a fantasy of some fans of esotericism, who seek hidden secrets in every symbol and doctrine. This tendency is intensified nowadays by New Age “esotericism of the masses” and by novels like those of Dan Brown, despite the fact that they lack any real foundation.
Many of those who call themselves “Christians,” actually aren’t (you can’t believe in Christ and at the same time affirm ideas opposed to his message, such as reincarnation). For Christians, the starting point of our faith is the acceptance of what God has revealed—not what He hides. For Christians who believe in Christ, God has already revealed everything necessary for the salvation of mankind.
Are there no secrets in Christianity?
It is true that every institution has some secrets in matters that require prudence and discretion. In this sense, we can speak of secrecy in the Church. But regarding religious content, Christianity is exoteric (open to all); it was born and continues to exist as a religion that is revealed for all people and sent to all people, universal (Mt 28:20 and following), missionary, and without secrets.
The Magisterium of the Church is composed of open, public documents, which anyone can read. Official declarations and doctrines are accessible to everyone. Everything is published, in matters of faith and doctrine. There is nothing that needs to be hidden. Esotericism—as an elitist spiritual attitude—is opposed to the nature of Christianity.
Throughout history, tendencies have arisen seeking to amalgamate gnostic and esoteric doctrines with Christianity, such as Gnosticism in the first centuries after Christ, the Medieval upsurge of alchemy and Kabbalah, and the occult movements of the Renaissance (16th century). These trends have influenced various intellectuals and artists. 
Their goal was to invent an “esoteric Christianity” or a “Christian esotericism,” and in fact there were—and are—esotericists who live a synchretistic form of Christianity. Consequently, symbols and concepts taken from alchemy and esotericism can be found in much literature, many works of art, and even in medieval churches.
But there has never been an esoteric form of Christianity, despite there being self-proclaimed “Christians” who, having forayed into esotericism, set out to give new meanings to the truths of the Christian faith, reinterpreting its symbols and doctrines, and professing “Christian esotericism,” which is a contradiction in terms.
Characteristics of Western esotericism
While there have been many and varied esoteric movements throughout history, we can distinguish some common or defining traits: 
1) Equivalence or coincidence between parts of the visible and invisible universe. For example: esotericists commonly refer to 7 metals, 7 planets, 7 parts of the body, 7 chakras, etc. When they read the Bible, they look for such coincidences, in order to interpret the bible “esoterically.”
2) They believe in that the universe and all of nature are a living being with a sort of cosmic soul (hidden fire or energy).
3) Creative imagination and symbolic mediation: They seek to reach the divine through imaginary or real intermediaries. This recourse to mediation of all kinds is clear to be seen: rites, symbols taken from all religions, mandalas, and even adopting every variety of supposed “spiritual entities.”
4) The experience of transmutation. This term, taken from alchemy, refers in this context to how a new way of living and being is sought through “initiations.”
There are other complementary characteristics that are not present in all cases, but which are very visible today in the great majority of known esoteric movements.
One such characteristic is the practice of concordance: the desire to harmonize different traditions, whether philosophical or religious—especially bringing together the oriental with the occidental. We can also add the direct transmission from master to disciple of esoteric theories and practices, which also often follows a series of degrees or steps in the process of initiation.
Among their key doctrines is a pantheistic view of divinity, according to which all reality is unified; from this follows an emanantistic idea of things and beings [all things “emanate” from God — translator’s note], in which there is no distinction between Creator and creature.
They proclaim the transcendental unity of all religions, which is to say, the idea that all religions agree on the deepest (esoteric) level, and that what matters most is this shared “mystical” nucleus, not the external forms of rites and doctrines.
However, anyone who really studies the great historical religions in depth, focusing on what are their truly central doctrines, will discover that they are radically different from each other. The ingenuous idea that all religions are really the same is a superficial thesis that ignores the actual nucleus of every religion. The external forms and universal ethical principles are precisely what tend to be shared among them, but not their deepest nuclei of belief.
The origin: A fantasy world
Although the adjective “esoteric” (hidden, secret) is very old and has had many uses, the noun “esotericism” appeared recently in the 19th century in the context of modern occult movements. 
Historically, there is no continuity from generation to generation in the western esoteric tradition, contrary to what its proponents argue on some occasions. Different historical epochs have seen a resurgence of similar ideas and religious reinterpretations, but without a real historical connection among them.
Although gnostic doctrines have disappeared for centuries at a time, they were influential during the Middle Ages through Hermeticism in alchemy, Kabbalah, and in certain philosophical schools. Similarly, they sought to influence Christianity, creating opposition to orthodox Christianity. A confrontation was inevitable, since the syncretism of these movements threatened to dilute the Christian faith in a pseudo-religious magma, as happened in the 16th century.
Today too, in the New Age movement, metaphysical and postmodern occult sects tend to present the Christian faith as an esoteric mysticism that was rationalized by the Catholic hierarchy. Ironically, their version of esotericism is contradictory to historical esotericism, since occult knowledge is elitist, and the New Age movement has popularized it for the masses.
While we can certainly speak of a serious effort to develop esotericism in the West (Boheme, Swedenborg, Paul Le Cour, etc.), it is not true that its origins are as historically remote as is presented in esoteric literature.
Most of the contents of these movements date from the Renaissance, yet seek to establish their origins in stories tracing back to ancient mythology, as is the case with some Masonic lodges, and above all, the Rosicrucians.
I say “some,” because many Masons recognize that Freemasonry originated in medieval guilds of stone masons, and not in the Tower of Babel, or Solomon’s Temple, or the Knights Templar, as some like to imagine.
One case of confusion created by esoteric literature, among others, is the Corpus Hermeticum, a work rediscovered by Ficino in the 16th century, written between the 2nd and 4th centuries, with Gnostic, alchemistic, oriental, esoteric, and Neoplatonic ingredients proper to the eclectic world of religions and philosophies that were in circulation in Alexandria in the 2nd and 3rd centuries .
Esoteric authors like to declare that this book is very ancient, offering dates such as the 6th century before Christ; however, it is a work written a thousand years later. Esotericism invariably claims to have roots where it has none, and tends to trace its genealogies back to remote ages in a mythology that is reinvented with each new generation of proponents.
René Guénon and the fraud of Theosophism
The Franco-Egyptian esotericist René Guénon was a great intellectual of modern occultism, respected not only for his erudition, but also for his academic honesty. He unmasked hundreds of fraudulent secret societies that made fools of their European initiates.
Guénon denounced and intellectually dismantled the fraud perpetrated by a woman canonized by occultism: Madame Blavatsky and her Theosophic Society . Nevertheless, people have short memories, which works in favor of pseudoprophets and their frauds, as has occurred with modern spiritism. Credulity continues to increase.
René Guénon abandoned western esotericism in the face of so much deception and fantasy, and ended up convinced that only oriental religions contain truly esoteric knowledge, as well as an authentic esoteric tradition.
One of the expressions of our current cultural crisis is the new emergence of Gnosticism and esotericism, manifested in the success of any and all literature related to these themes—magic, the apocryphal Gospels, self-help, alchemy, Hermeticism… If the true history of esotericism were better known, its magical illusions would disappear all too quickly.
What of those who call themselves “Christian esotericists”?
Many modern-day esotericists speak openly about “Christian esotericism,” but it is simply their reinterpretation of Christianity, just like their reinterpretations of certain ancient philosophical currents or religions of the Orient, which they appropriate carelessly according to their personal taste.
The fact is that Christianity was never esoteric, and its very missionary nature makes it an open religion, whose message is for everyone, and not for an elite that seeks symbolic coincidences or invisible worlds.
No one can deny that throughout history there have been people who live Christianity on a social level but who practice esotericism, and it continues even today. In the Middle Ages, even among people who were officially Christian, Jewish, or Muslim, Gnostic and magical currents of thought subsisted and experienced occasional resurgences.
Faced today with esotericism for the masses, we should ask ourselves if Christianity might not have neglected its own measure of mysticism and mystery. Perhaps it has gone overboard in its rationalistic adaptation to modernity, and consequently, people thirsting for meaning and experience have turned to irrationalism, magic, and the occult.
 ELIADE, Mircea (1976). Occultism, Witchcraft and Cultural Fashions. New York: The Crossroad Publishing Company.
 GUERRA GÓMEZ, Manuel. (2005). Diccionario enciclopédico de las sectas. Madrid: BAC.
 FAIVRE, A. – NEEDLEMAN, J. (1995). Modern Esoteric Spirituality. New York: The Crossroad Publishing Company. p. 10 [Spanish edition]
 See ELIADE, Mircea (1969). The Quest: \ History and Meaning in Religion. London: University of Chicago Press. Pages 59-60 [Spanish edition].
 GUENÓN, René (2003). Theosophy: History of a Pseudo-Religion. New York: Sophia Perennis Haz.