From an engineering point of view, a scientific theory does not have to be true.  It just has to be useful. 

Hello John,

a bold statement ;-)

But it is true that for an engineer the priority is that it works, knowing how it works is a bonus, while for a scientist the last is the most important.

Being a (lonely) engineer working with scientist I sometimes try to explain the difference between a scientist and an engineer this way:

When a scientist builds a bridge it will collapse, but the scientist can perfectly explain why it collapsed. When an engineer builds a bridge it will not collapse, but the engineer will not have a clue why it does not collapse.

73, Rik  ON7YD - OR7T