  Mathematicians manipulate sets with confidence almost every day, rarely
making mistakes. Few of us, however, could accurately quote what are often
referred to as "the" axioms of set theory. This suggests that we all carry
around with us, perhaps subconsciously, a reliable body of operating principles
for manipulating sets. What if we were to take some of those principles and
adopt them as our axioms instead? The message of this article is that this can
be done, in a simple, practical way (due to Lawvere). The resulting axioms are
ten thoroughly mundane statements about sets.
  This is an expository article for a general mathematical readership.
