The FAA regulates logging time in FAR 61.51. There are plenty of questions about logging PIC time, as well as SIC time. Another type remains: what can be logged as total time? It's only mentioned once:
Total flight time or lesson time.
It is clear that any time logged as dual, PIC, or SIC can be logged as total time. Is total time merely the sum of those, minus any overlap, or is there a situation where total time can be logged but none of the others?
In particular, two situations arise:
I'm at the controls of an aircraft I'm not rated for (i.e. an ASEL pilot in the right seat of a multi-engine aircraft, where the other pilot is appropriately rated and not a CFI). I can't log PIC, SIC, or dual - but can I log total time?
In a plane I'm rated for, I pass the controls to a non-certificated passenger. I'm not a CFI. I cannot log PIC, SIC, or dual while my passenger is the sole manipulator of the controls, but I am acting as the PIC for this portion of the flight. Can I log this as total time?