All I'm saying is that if Spirits are physical manifestations of a former human or a telepath's subconcious, then it would make very little sense for them to have literal strength -- after all, what is strength but the amount and condition of muscle fibre in the body, and by extension the ability of mitochondria to manufacture ATP from glucose through complete respiration? -- but do spirits eat? No.
So, I turn to Sherlock Holmes on this one: "How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?"
And yes, of course I've heard that other quotation. What kind of Duck would I be if I hadn't?