Mumler was just the Middleman
Mumler’s images were the intimate images spiritualists were hoping for; ghostly figures not just appearing in the frame, but actually appearing to touch or embrace the living. For people who needed to believe their loved ones were still with them, or at the very least, that there was life beyond death, this was proof. The photographer was careful not to guarantee a spirit would appear. He never claimed to be able to summon spirits, nor summon specific spirits. Some of his photographs may not have a spirit at all. Others may not be the spirit the subject was hoping to see. Spirits were free to move in and out as they pleased, so if a client didn’t recognize the spirit in the image, well, that wasn’t exactly Mumler’s fault. He was a medium, able to channel the spirit world, not command it.