xxiiSuch phenomena are what Ãcariya Mun called “mysteries of
the heart”; for they are conscious, living beings dwelling in spiritual
dimensions that are just as real as the one we inhabit, even though
those spheres lie outside the realm of human existential concepts. The
words “heart” and “mind” are used interchangeably in Thai vernacu-
lar. “Heart” is often the preferred term, as “mind” tends to exclude the
emotional and spiritual dimensions associated with the heart. The
heart is the essential knowing nature that forms the basic founda-
tion of the entire sentient universe. It is the fundamental awareness
underlying all conscious existence and the very basis of all mental and
emotional processes. The heart forms the core within the bodies of
all living beings. It is the center, the substance, the primary essence
within the body. Constantly emphasizing its paramount significance,
Ãcariya Mun always claimed that the heart is the most important thing
in the world. For this reason, the story of Ãcariya Mun’s life and teach-
ings is a story of the heart’s struggle for spiritual transcendence, and
a revelation of the ineffable mystery of the heart’s pure essence.
The Pãli term “citta” is a word that Ãcariya Mun often used
when referring to this essential knowing nature, commonly known
as heart and mind. Like so many words in the Buddhist lexicon, it is
essentially a technical term used specifically in the science of Bud-
dhist theory and practice. Since such terms represent salient aspects
of the subject matter of this book, some of them have been kept in
their original form. Generally, in cases where a suitably accurate
English translation exists, that word has been substituted, with the
Pãli term in question being annotated in an explanatory note. There
are, however, certain terms for which, due to the complex and com-
prehensive nature of the truths they represent, no truly adequate
English word exists. Those specialized terms have largely been left
in the original Pãli. They may be found explained in the Notes and
Glossary sections at the back of the book, and the reader is encour-
aged to take full advantage of these reference materials.