 A weak point of Fechner’s argument is that he never sufficiently clarifies what he means by the soul or mind. His argument is cast in the language of having “a soul”, which makes it seem as if he means a special kind of substance. He tells us that by a soul (Seele) he means the same thing as mind (Geist); but this only kicks the can down the road: What are the criteria of a mind? The crucial consideration for Fechner seems to be sentience, consciousness or awareness, or at least the possibility of it. Even the most primitive plants, he argues, have consciousness or feeling; though it might not be on the level of humans and animals, it is still at least as lively and intense (Nanna: 188). This is interesting because Fechner seems to exclude the possibility of the subconscious; he does not allow, as Leibniz famously did, the existence of subconscious living creatures. In some places, Fechner seems to hold that having feelings and desires are sufficient for the presence of a mind; but he also writes that there can be sensation and desire without consciousness (Nanna: 53). In other places, he makes purposive activity a necessary condition of having a mind. Only a being with a soul has a purpose, he says (Nanna: 152). The crucial consideration for an organism, he also contends, is that its organization allows it to effectively achieve its ends (Nanna: 191). But this too becomes troubled because Fechner concedes that there can be purposive or organic development without any awareness of it (Nanna: 87).