Heh. Empathy doesn't have to be so nebulous. It may be a sixth sense but there has to be something to sense. Otherwise it wouldn't be a sense. I can think of four ways off the top of my head. Mentally, being able to read the particulars of the brain that revolve around emotion; chemically, able to pick up the subtle chemical scents that the body gives off; thermally, able to sense and interpret the areas of the body that heat up and cool down with particular emotions; and perhaps the more difficult to explain aurally, the ability to sense the aura (one could say spirit) that surrounds every living being.