According to tradition, Nichiren's six senior disciples collected his writings at Ikegami in Musashi province on the
first anniversary of his death.  These works were called the "rokunai gosho" (cataloged writings).

A year later, they were said to have gathered those writings that had eluded their first compilation effort, terming these works the
"rokuge gosho" (uncatalogued writings).  Nikko would have
participated in both of these efforts.

The entire "rokunai" collection did not appear in its
entirety until the Genna Era (1615-1623) and the "rokuge"
collection in Kanbun 2 (1665).  Early on, scholars
recognized that in the course of this long compilation
process, works written by individuals other than Nichiren
himself had been incorporated into the collections and
transmitted as authentic works of Nichiren himself.
Forgeries became a problem early on.  Nikko, in his "Nikko
yuikai okibumi" (Nikko's last admonitions), traditionally
dated 1333 (the year of Nikko's death) warns against
associating with those who forge gosho and condemns them as
"parasites in the body of the lion".

Yamakawa Chio (1879-1956) proposed a basis for
distinguishing the forged from the genuine writings by
assembling all the reliable documents in Nichiren's own
hand, assembling them in chronological order and then using
then as a "normative gosho" against which questionable texts
might be evaluated.  Another scholar, Suzuki Ichijo,
proposed that the "authenticated works must be writings that
[are in ] Nichiren's own handwriting.  Writings of doubtful
authenticity have been incorporated in the "rokunai, rokuge
and later collections of complete works".  These must be
investigated and removed, if found to be forged, to protect
the purity of the body of Nichiren's authentic works."

Taisekiji has assumed that the essence of Nichiren's
doctrine was expressed in those works that reflect the
influence of "medieval Tendai(chuko) original enlightenment
thought".  But these works were not, in reality, written by
Nichiren.  They often go against the strict doctrinal
positions that are the basis of the five major works of
Nichiren (which are undisputedly authentic).  At least 55
gosho, reflecting this "chuko Tendai" represent the
forgeries of later disciples.  Such works as the
"Kechimyaku" gosho, the "Abutsubo" gosho, the "Shoho Jisso
sho", "Issho Jobutsu Sho"...even the "San dai Hiho Sho" are
listed among the questionable works which are probably
forgeries.  These works do not exist in Nichiren's hand, the
copies are far removed from the time around the six senior
disciples and these works borrow heavily from "chuko Tendai
original enlightenment thought".  This "original
enlightenment thought" is different from the "original
enlightenment thought" of earlier Tendai thinking that
Nichiren was educated in.  The "chuko Tendai" tradition
adulterated Lotus doctrine with elements from Zen, Pure Land
and Shingon, thus mixing the pure with the provisional.
After the early period of Nichiren's authenticated works
(1242-1260), few of his authentic writings have original
enlightenment thought as their central theme.  Moreover, the
forged works employ certain terms and expressions that do
not appear in Nichiren's genuine writings.  This terminology
didn't even fully develop until after Nichiren's death.

Herein lies the principle of "textual parsimony", the basing
of interpretive work solely upon undisputed texts.  The fact
that so few of Nichiren's genuine documents deal with
"original enlightenment thought" constitutes a powerful
argument.  Over a hundred genuine works of Nichiren survive
in his own hand.  Others are copies by reliable sources,
usually associated with close disciples.

Asai Endo ,an eminent scholar, holds that medieval Tendai
stressed only the Buddhahood inherent in ordinary people and
"disregarded even the [stage of] hearing the Dharma and
embracing it with faith," which he terms "a confusion of
theory and practice."  Nichiren is presented as a teacher
who championed the return to orthodox centrality of
practice, rejecting the purely theoretical identification of
the Buddha and the ordinary person, as set forth in medieval
Tendai.  Where medieval Tendai emphasized originally
inherent Buddha nature (bussho), Nichiren stressed receiving
the seed of Buddhahood (busshu) in the act of chanting the
daimoku.  Medieval Tendai placed emphasis on innate
Buddhahood , and Nichiren, on accessing it in the act of
practice.

Of the fourteen writings addressed to Sairen-bo, none
survive in Nichiren's own handwriting.  Very little is known
about Sairen-bo's biography.  All the works addressed to
Sairen-bo focus on concepts related to Medieval Tendai
original enlightenment thought.  "ShohoJissho Sho" ("True
Entity of life", or, more accurately translated, "The
reality of the Dharmas") is one of the writings that is
thought to be a forgery.

So, the lack of a surviving holograph (i.e. written in
Nichiren's own hand), or other independent verification, and
the use of terminology related to "chuko Tendai original
enlightenment thought" are serious considerations in
assessing Nichiren's actual thinking.  Hence, it is prudent
to focus on the authenticated writings of Nichiren, then
branch out cautiously to the questionable writings and judge
their merits against the standard of the major works of
Nichiren, such as the "Kanjin Honzon Sho", "Kaimoku Sho",
"Senji Sho", "Ho'on Jo" and "Rissho Ankoku Ron".