Or, conversely, can a thought exist without a material brain to think it? So would I, but there's plenty of sound evidence that would, reasonably and rationally, disagree. OK. I've never thought of listing ... I wonder if it's one of those 'how many angels on the head of a pin' type questions? A thought. A memory. Are they the same substance? I don't have answers ... I'm just musing. I'd start with terms from Scripture: nefesh (Hebrew) | psyche (Greek) | anima (Latin) The animal or sanguinary soul, every 'living' thing has this. "for the life (nefesh) of every creature is the blood of it" (Leviticus 17:14) "for the blood is the life (nefesh)" (Deuteronomy 122:23). ruach | nous/pneuma | spiritus The term 'ruach' means 'breath' (in the anthropological sense) or 'wind' (in the spiritual), and as such can express the principle of life, rather than an individual being: "In whose hand [is] the soul (nefesh) of every living thing, and the breath (ruach) of all mankind" (Job 12:10) Ruach can imply a meta-personal quality, not necessarily above the cosmological. In reference to God it signifies the Divine, but in reference to the spirit of man, not necessarily, it's fallible: "They also that erred in spirit (ruach)" (Isaiah 29:44); it can signify disorder, passion, even madness, "Terrors are turned upon me: they pursue my soul as the wind (ruach)" (Job 30:15), or "Behold, they are all vanity; their works are nothing: their molten images are wind (ruach) and confusion" (Isaiah 41:29). Neshamah| (pneuma/pnoe | spiritus/spiraculum/habitus) The breath, be it human or divine. In Genesis God made man and 'breathed' life into him. The Divine Breath not only animates, it can also confer a sanctified state, a state of grace. I presume Islam has its own hierarchy? I know of ruh and nafs only in passing, but is there not a link to the Hebrew?