The album features twenty-five songs that had never been released, and early alternative renditions of "The Street Only Knew Your Name" from Inarticulate Speech of the Heart, "Wonderful Remark" from The Best of Van Morrison, "Real Real Gone" from Enlightenment, "Joyous Sound" and "Flamingos Fly" from A Period of Transition, and "Bright Side of the Road" from Into the Music.

"Twilight Zone", "Foggy Mountain Top" and "Flamingos Fly" were all mixed in 1974 just before Mechanical Bliss was due to come out.

When it was released, some of the tracks had been changed; "When I Deliver", "John Brown's Body" and "I'm Ready" were replaced by "The Street Only Knew Your Name", "Western Plains" and "Joyous Sound".

[5] Commenting on the previously unreleased songs, Van Morrison remarked: "It's hard to work out why you didn't put something out at the time.

[6] Scott Thomas in the fan magazine Wavelength noted: Everything about The Philosopher's Stone, from its format to its packaging to its song selection, seems designed to divorce the tracks from their historical milieu...When we open the package, there are no essays, no interviews, no archival photos — just lyrics (often incorrectly transcribed) and credits which include the year of the session.