#1: Harmony and Discord

Bitcoin experts talk often of consensus, whose meaning is abstract and
hard to pin down. But the word consensus evolved from the Latin word
concentus, "a singing together, harmony,"^[1] so let us talk not of
Bitcoin consensus but of Bitcoin harmony.

Harmony is what makes Bitcoin work. Thousands of full nodes each work
independently to verify the transactions they receive are valid,
producing a harmonious agreement about the state of the Bitcoin
ledger without any node operator needing to trust anyone else. It's
similar to a chorus where each member sings the same song at the same
time to produce something far more beautiful than any of them could
produce alone.

The result of Bitcoin harmony is a system where bitcoins are safe not
just from petty thieves (provided you keep your keys secure) but also
from endless inflation, mass or targeted confiscation, or simply the
bureaucratic morass that is the legacy financial system.

Discord

Discord is the enemy of harmony. If, in the great chorus of Bitcoin full
nodes, half the singers decided to suddenly switch tunes, the harmony
would be lost. In its place would be two smaller singing groups who try
to out sing each other (or who may compete through less scrupulous means),
leaving everyone worse off.

This is what a contentious hard fork has the potential to do.  Some
people will program their full nodes to sing one song; other people will
program their full nodes to sing a different song.  In the cacophony
that results, there will surely be confusion, recriminations, and loss
of confidence.

For this reason, contentious hard forks are to be avoided.

But this doesn't mean we have to sing the same song forever. We have
other options. The first is gathering widespread agreement to change to
a new song---to hard fork the system without giving discord a foothold.

The second way is to add new layers to the existing harmony.  A chorus
will often sing accompaniment to an orchestra, and together they can
entertain audiences neither of them could have pleased alone.  Soft forks
are the preferred method for adding new features to Bitcoin because they
allow old nodes to continue to sing the same old song (unless they're
miners), while new nodes get to partake in the expanded choices.

Given two forking paths to the same feature, a soft fork is the safer
option because it leaves no room for discord, and no risk that the
essential harmony that underlies Bitcoin's security will be lost.