Reading guide
A shift from substance to duration
Every discourse before this one measured an accumulated quantity — wood, earth, milk; this discourse instead measures how long a single unit of time, one eon, actually lasts.
A precise, almost architectural image
The mountain is specified with exact dimensions — a league long, a league wide, a league high, solid with no cracks or hollows — giving the simile a concreteness that makes the erosion that follows feel genuinely physical.
Erosion by the gentlest possible touch
The mountain isn't blasted or carved; it's stroked with a fine cloth, once per century — the almost imperceptible gentleness of the method makes the eventual total erosion even more striking than a violent one would.
An eon exceeding even this exhausted mountain
The punchline isn't simply that the mountain wears away; it's that the mountain would be completely gone before the eon itself comes to an end — the eon outlasts even total geological erosion.
Many eons, not merely the one just measured
The discourse's final move extends beyond a single eon's length to the sheer number of eons already transmigrated through — setting up SN 15.6 and 15.7's direct treatment of that even larger question.
Key terms
The text
§1At Sāvatthī. Then a mendicant went up to the Buddha, bowed, sat down to one side, and asked him, “Sir, how long is an eon?” “Mendicant, an eon is long. It’s not easy to calculate how many years, how many hundreds or thousands or hundreds of thousands of years it lasts.”
§2“But sir, is it possible to give a simile?” “It’s possible,” said the Buddha. “Suppose there was a huge stone mountain, a league long, a league wide, and a league high, with no cracks or holes, one solid mass. And as each century passed someone would stroke it once with a fine cloth from Kāsi. By this means the huge stone mountain would be worn away before the eon comes to an end. That’s how long an eon is. And we’ve transmigrated through many such eons, many hundreds, many thousands, many hundreds of thousands. Why is that? This transmigration has no known beginning. … This is quite enough for you to become disillusioned, dispassionate, and freed regarding all conditions.”
Self-check quiz
Ten questions. Click an answer to see immediate feedback. No score is recorded — this is for your own checking.