# Why does the high level threshold level for quorum have to be above 66%?

What is reason that the threshold of consensus bearing nodes must be above 66% for the network to operate successfully?

This is straight from the docs of the stellar-core_example.cfg file.

UNSAFE_QUORUM (true or false) - default false

Most people should leave this to false.

If set to true allows to specify a potentially unsafe quorum set. Otherwise it won't start if a threshold % is set too low (threshold below 66% for the top level)...