Board Thread:Warhammer 40k General Discussion/@comment-72.129.239.20-20140901022712/@comment-25073042-20140901064405

The machine spirit could be, like you said, something like "we don't really know how this works, so it must be working because of spirits". But it also could be the influence of the (probably) Void Dragon C'tan that the Adeptus Mechanicus worship as the Machine God. Personally I think that in most cases it's the former.