Translation of excerpts from L’Art Idealiste et Mystique (Doctrine de l’Ordre et du Salon Annuel du Rose + Croix), 1894.
Artist, you are a priest: Art is the great mystery and, if your effort results in a masterpiece, a ray of divinity will descend as on an altar. Artist, you are a king: Art is the true empire, if your hand draws a perfect line, the cherubim themselves will descend to revel in their reflection. Spiritual design, a line of the soul, form of understanding, you make our dreams flesh. Artist, you are a mage: Art is the great mystery, it only proves our immortality.
Who still doubts? Giotto touched the stigmata, the Virgin appeared to Fra Angelico, and Rembrandt demonstrated the resurrection of Lazarus. [This is] the absolute rejoinder to pedantic quibbles : we doubt Moses, but here is Michaelangelo; we misunderstand Jesus, but here is Leonardo; we secularize everything, but immutable, sacred Art continues its prayer.
Unspeakable and sublime serenity, ever-shining Holy Grail, ostensorium and relic, unvanquished sacred banner, all-powerful Art, the Art God, I adore you on my knees, you, the final reflection from on High over our putrescence.
All is rotten, all is finished, decadence has cracked and shaken the Western edifice, and the lonely cross no longer has the Guise sword or a Royalist rifle beside it. Weep, Gregory VII, oh immense pope, you who had saved everything, weep from heaven for your Church that is now in shadows, and you, old Dante, get up from your throne of glory, you Catholic Homer, and join your anger with Buonarotti’s despair.
Yet a glimmer of Holy Light, a pale glow appeared, and grew… And thus on the gallows of the holy torment, there blossomed a flower.
A miracle! A miracle! A rose emerges and opens as it grows, endeavouring to grip the divine cross of salvation in its pious leaves: and the cross, consoled, is resplendent: Jesus has not cursed this world, Jesus receives the adoration of Art.
The Mages, the first ones,came to the divine Master.  The last Mages are their sons.
Pitiful moderns, your course into nothingness is fatal; fall then, under the weight of your worthlessness: your blasphemies will never erase the faith of works of art, you sterile ones!
You may one day close the Church, but [what about] the Museum? If Notre-Dame is profaned, the Louvre will officiate… Humanity, oh citizens, will always go to mass, when the priest will be Bach, Beethoven, Palestrina: one cannot make the sublime organ an atheist! Brothers in all the arts, I am sounding a battle cry: let us form a holy militia for the salvation of idealism. We are a few against many, but the angels are ours. We have no leaders, but the old masters, up there in Paradise, guide us towards Montsalvat… This precious Church, the last august thing in this world, banished the Rose and believes its perfume to be dangerous. Next to it then, we will build the Temple of Beauty; we will work to the echoes of prayers, followers, not rivals, different,
not divergent, for the artist is a priest, a king, a mage, for art is a mystery, the only true empire, the great miracle… Jesus has not cursed this world. Jesus receives the adoration of art. The noble enthusiasm of the artist will survive beyond extinct, erstwhile piety.
Theory of Beauty
A. I. There is no other reality than God. There is no other Truth than God. There is no other Beauty than God.
God alone exists, and any word that does not express this is a noise, and every path that does not seek him leads to nothingness. The only end of mankind is the quest for God. He must perceive Him, conceive Him, hear Him, or perish in ignominy.
A. II. The three great divine names are: 1. Reality, the substance or the Father; 2. Beauty, life, or the Son, 3. Truth or the unification of Reality and Beauty, which is the Holy Spirit.
These three names govern three ways to the same end,  three quests for God, three religious modes. [You should] understand “religion” in the sense of [that which] connects the creature to the Creator.
A. III. Science, which seeks God through Reality. Art, which seeks God through Beauty. Theodicy, which seeks God through Thought.
What, then, is Beauty? If not…
A. IV. The quest for God through Life and Form.
But, even as the three divine persons are all present in each other, thus Beauty is specified in three rays, forming the triangle of Idealism.
A. V. The Beauty of the Father is called Intensity. The Beauty of the Son is called Subtlety. The Beauty of the Holy Spirit is called Harmony.
If one calls something ideal, that is to attribute conceivable intensity, subtlety and harmony to it; and art, considered in its essence, is that which defines it.
A. VI. The esthetic point of a form is the point of apotheosis, which is to say the realisation that it is approaching the perceivable absolute.
A. VII. Manifest intensity is called the sublime. The sublime is achieved by an excess of one of the proportions, and it operates on the aesthete through surprise/wonder: as in the lowering of temples in the Orient and the elevation of arched cathedrals; or Michaelangelo in both his arts.
A. VIII – Manifest Subtlety is called Beautiful; Beauty is achieved by weighting and the equilibrium of the most immediate relationships [of form], such as Raphael’s School of Athens.
A. IX. Manifest Harmony is called Perfection,  and it is achieved through weighting and balancing all relationships, even the most asymptotic, such as in the work of Leonardo da Vinci.
The Rose + Croix class all the categories of understanding as subdivisions of a unique science: theodicy…
The reader should never forget, over the course of these pages, that Art is presented here as a religion or, if you will, as that part of religion that mediates between the physical and the metaphysical.
That which distinguishes a religion from a philosophy, is the dogmatic absolutism and canonical ritual: it is the subordination of individualism to a collective harmony.
What dogma is applicable to all the design arts? What is the essence of Art? And how could one define Art itself, if not thus:
A. X. Art is the totality of the methods of realising Beauty.
A. XI. Beauty is the essence of all expression through form.  Techniques are nothing more than the means to an end.
If Beauty is the objective, and art the means, what is the rule? The Ideal.
Open a Littré dictionary at this word: “Ideal; that which reunites all the perfections that the spirit can conceive”.
THEREFORE IDEALIST ART IS THAT WHICH REUNITES WITHIN A WORK ALL THE PERFECTIONS THAT THE SPIRIT CAN CONCEIVE ON A GIVEN THEME.
One may already understand that there are themes which are too low to sustain any idea of perfection, and that I have reviled, with absolute logic, from the Salons of the Rose + Croix […]
Wagner says in one of his theoretical writings:
“Art begins where life ends”. Because the same woman, whom lust greets with desire, does not solicit admiration through her reproduced image. This is why, after the first adjective: idealist, I had to add another: mystical.
For “mystical” means that it holds mystery, and a mystic is an initiate.
It is not therefore enough for a work to satisfy the idea, it must also determine an impression of the beyond, it must be a springboard of enthusiasm, a determinant of thought. Generally, Titian is ideal, but never mystical; the opposite appears among the Trecentisti, always mystical, rarely ideal.
A. XII. The Beauty of a work is made from sublimated reality.
A. XIII, The mysticism of a work derives from the depiction of the unreal [Translator's note: Read visionary].
A. XIV. A work that is real in form, and unreal in expression, is perfect: Leonardo.
These antique principles, forgotten today, disdained, presided over ancient genius.
Plato alone dared to consider Beauty as a spiritual being that existed independently from our conceptions: and an unjustly forgotten thinker, Maximus Tyrius, showed in the 2nd century (he lived in Rome under Commodus) that the tradition lived on:
“Ineffable beauty – he said – exists in the sky and in the planets. There, it remains unadulterated. But in coming to earth, it is obscured by degrees… He who maintains the essential notion of Beauty in his soul will recognise it when he sees it: like Ulysees recognised the smoke rising from his ancestral home, the aesthete quivers, joyful and moved. A majestic river, a beautiful flower, a fiery horse certainly offer some snippets of Beauty, but they are very crude.
If Beauty descends, to some degree, into matter, where would we see it if not in man, whose soul follows the same principle as Beauty?
Beauty is something that is more alive, it does not spend time on games, it brings ecstasy.Our souls exiled on earth, enveloped in thick slime, are condemned to an obscure life, disorderly, full of troubles and bewilderment, they cannot contemplate ineffable Beauty with energy and fulfillment. But our soul leans perpetually towards order and towards beauty. Moral or spiritual order , just like physical, or natural order, constitutes the beauty with which [our souls] are in eternal sympathy.
Therefore, here is a philosophy that validates my use of the terms “idealist and mystical”:
A. XV. The ideal, is the pinnacle of a form.
A. XVI. And the mysticism of a form is its nimbus, its countenance of the beyond. The beautiful form in itself, the ideal, is susceptible to two augmentations, as told by Maximus Tyrius in his 25th thesis:
“The beauty of the body cannot be beauty par excellence, it is none other than, in some way, the prelude to a more complete beauty.”
In each of the three formulae of Beauty, there three further degrees, just as there are three elements in man.
Intensity, subtlety and harmony give way to three aesthetic results.
The sublime may be physical, like the torso palpated by a blind Michaelangelo; animistic, like Laocoon; spiritual, such as the Genius of eternal rest (« Narcisse », dit « Hermaphrodite Mazarin » ou le « Génie du repos éternel » ).