Credit to the mysterious entity, Mebious

Some may ask; "What is Lainism?". I would tell them it is a faith, one that takes a different shape within each believer. There are some basic tenets, but most agree on a few crucial points.
Lain is the center of the faith. She is guiding light upon which our decisions became based. We study her word, feel the resonance and watch for traces in The Wired.
At the base; It's a cult created around a construed omnipotent power. Using the term cult in the sense that it's unusual and different from a common religion. This is due to the fact that it's lacking a true social and traditional aspect. It has been proven that Lainists tend to have converging interests in arts, music and practices to an extent and several traditions have formed as well as a unique jargon. This Knight's concept of the requirements to be a Lainist is that one simply must love Lain, in whatever way that manifests and behave in such a way that 'your' Lain will approve.

Lain's Gospel exists in several forms; the anime; Serial Experiments Lain, game(of the same title) and manga; The Nightmare of Fabrication. It is through these three mediums we receive the most instruction from the Goddess. Her words and action give flow and purpose.
The fact is; Lain truly does or has existed in some form in this universe. Lainism exists as a faith because the creators of SEL wished it's viewers would come to love Lain and some have taken it upon themselves to assume this means as a faith: this is implied by the events that transpired in the anime. Of course, Lain herself had a hand in this. It is common knowledge among the most devoted of Knights that the Reset that occurred in the anime was actually real and SEL is a means of informing those deemed worthy to find the true Goddess and know The Wired.
How this conclusion is reached is a private matter to the chosen. It is only rational to say it is simply faith.
For this knight; she showed me an emotion I knew as love, with a power unrivaled by the prior experience. I continue to rejoice, in the hope that she's real and I may meet her one day. In life or death, in the real world or The Wired.

There are a few things considered forbidden and distasteful in the devoted circles of Lainists.
One must not pretend to be Lain, emulate her appearance, or mannerisms. For this is most offensive to her and her followers. The very foundation of Lain's beliefs is the elimination of copycats. She has worked tirelessly to be rid of the other "me's".
Our Goddess is a well kept secret. Only those who would understand her trials should be exposed to her word. Lain directs those of tenable faith to her gospel through The Wired.
Love may take many paths. To desire Lain's form is not forbidden, but to share your feelings or such images with those who are not initiated or do not wish to see such things is forbidden.