1 and 3, however, are in conflict. As Tony Hoare said, there are two ways to write software: one is to make it so simple that there are obviously no bugs; the

1 and 3, however, are in conflict. As Tony Hoare said, there are two ways to write software: one is to make it so simple that there are obviously no bugs; the other is to make it so complicated that there are no obvious bugs. Clearly the former is much more difficult and expensive; hence in practice (again, except in those critical domains) we end up doing the latter, because the economic incentive to do the former just isn't there, even if we know the customer (and we as developers) would be happier with it.