The series involves several religious and philosophical themes, including references to the work of Pierre Teilhard de Chardin.
The series begins with Intervention: A Root Tale to the Galactic Milieu and a Vinculum between it and The Saga of Pliocene Exile (ISBN 0-395-43782-2, Boston: Houghton Mifflin, 1987).
The most notable example occurs in the first part of Chapter 24 of Jack the Bodiless, where Teresa Kendall explains Christianity to her unborn son.
Jack the Bodiless begins with a set of quotations, including the Spanish proverb "God writes straight with crooked lines."
This proverb summarises the plot of the whole series, in which tragedies and disasters (particularly the Metapsychic Rebellion) result in ultimate good (particularly the repentance and transformation of Marc Remillard, through which the Galactic Milieu is formed).
Julian May's description of "metapsychic" abilities explicitly refers to the concepts of auras (particularly in Part III of Intervention) and chakras (particularly in discussing the feeding of the "Hydra").
The Lylmik (LIL-mik[3]) are the oldest race in the Galaxy, having been shepherded to mental Unity or "coadunation" by the entity known as Atoning Unifex.
The Krondaku (krah'n-DAH-koo[3]) are large tentacled invertebrate "monsters", the Gi (ghee[3]) are feathered hermaphrodites with a well-developed aesthetic sense, the Simbiari (sih'm-bee-AH-ree[3]) are green and slimy, while the Poltroyans are small purple humanoids who most resemble human beings both physically and mentally.
A metaconcert is a synchronized use of mental powers by more than one person, in which the whole is greater than the sum of its parts, as when Jack and Dorothea tackle the geological problems of Caledonia.
Don is distrustful and malicious, but handsome and charming, and steals Rogi's girlfriend Marie Madeleine "Sunny" Fabré.
Denis is a precocious child, and quickly learns to master many metapsychic faculties, greatly exceeding those of Rogi and Don, in addition to excelling intellectually.
Meanwhile, Don and Sunny raise their nine other children, including the monstrously evil second-born Victor, who terrorizes his younger siblings and suppresses their mental powers.
Subsequent research yields results in many places in the world and Denis organizes yearly meetings within the secret metapsychic community.
This culminates in a showdown at the end of the book where Denis calls out to all the present and absent metapsychics of goodwill to join in a "metaconcert" against an attack by Victor and Kieran.
Marc, Paul's firstborn with his wife Teresa Kendall — a grandchild of Don's via Rogi's former lover, Elaine, is the most powerful human metapsychic known at that time, who also has a genius-level intellect.
Sometime later Teresa regains her voice and becomes illegally pregnant with the last of their children, and when Marc farsenses emotional problems over her pregnancy he visits his mother to investigate.
Upon learning of his mother's pregnancy, Marc takes it upon himself to hide Teresa and his future brother in the icy Canadian wilderness.
Although Jack has the outward appearance of a normal human child, his intellect and mental prowess rapidly set him apart from the rest of humankind, as does the fact that his body begins to generate inoperable and incurable tumours that are slowly overwhelming him.
Despite the fact that Jack possesses each of the five higher mindpowers (also known as metafaculties) at the highest known level (Paramount Grand Master), he is incapable of effecting change in his own physiology.
When his rival's wife is killed after being shoved into a trash compactor in an apparent suicide disguising her murder by Hydra, a hold is put on Human entry into the Milieu for 1,000 Galactic Days.
Dorothea turns out to be another Paramount, with incredibly strong redactive powers and resistance to metapsychic probes and attacks.
Dorothea and Jack have a role in saving an inhabited planet from a diatreme eruption, using their paramount powers aided by CE.
But her lower face is terribly deformed in this heroic act, so after this she always wears a diamond-studded half-mask, and acquires her nickname "Diamond Mask".
It would use selective breeding, surgical modification, mental training (through induced pain) and technological enhancement to create hundreds of humans with the powers — and disembodiment — of Marc's younger brother Jack.
Marc's increasing ambition draws him to side with a rebel faction of the Concillium — those that do not wish to join 'Unity' with the other races and therefore with the Galactic Mind itself.