What does it mean to be immaterial? Can we say that being immaterial means that one is animated and possesses a personality (or in other terms, that a thing is immaterial if it is animated and is a person.)?
A preliminary problem that I see with this idea is that it seems that ideas, concepts, mental images and imaginations, dreams, essences, natures, etc., are all immaterial, yet none of these things can be said to be either animated or possessing a personality. On the other side of the picture, it seems that we run into things that are both animated and in possession of a personality every day, yet they are obviously not immaterial - humans. If we treat animated and personality separately, then we see that being animated does not mean that one is immaterial (The word animated comes from the Greek anima which roughly translated means soul or source of life). Robots are "animated", and yet they are quite material. However, there is a difference between robots and animals. Animals are "self-animated", in otherwords, they are, in a sense, the source of their movement. There is also a difference between animals and humans. Humans are "self-animating and self-directing" (in other words, humans choose their ends). Yet, though all three groups (robots, animals and humans) are animated, they are all, also, material. (Humans alone, of the three groups, have a personality.)
That being said, there is more to plants, animals and humans than meets the eye. Rocks, Ipads, dirt, dead bodies, etc. are not animated; neither can we say that they have a personality, or that they are persons. Yet they are like humans in that they are material. What is it that makes the difference between rocks and humans? Materialists say that it is the combination of molecules. However, if it was just the combination of molecules, then why is a corpse not capable of self-animation? The human corpse possesses all the right molecules, and the right parts (in fact, the most obvious difference between a human corpse and a living human is that the living human possesses self-animation and self-direction, whereas the human corpse possesses neither), yet it is obviously not a human. If Materialism is true, then, strictly speaking, Frankenstein should not be a fiction. We should be able to go into any grave yard, assemble the right parts, add electricity and cause human life. Yet, inspite of all our technological advances this is not happening. Why not?
It seems that there is something more to plants, animals and humans then just molecules and energy. Traditionally, in the aristotelian tradition, we call this the soul (or the form). The soul is the source of life - the source of animation in all animated things. Yet, plants, animals and humans are not, because they have a soul, immaterial. They are composed of form and matter (soul and body). It is this composition that makes these things to be what they are. (A related question concerns angels. Angels do not have matter, therefore they are immaterial. Strictly speaking, even rocks, dirt, and corpses, are composed of form and matter, yet they do not have a substantial form, only an accidental form. For more on this subject see my blog post here, here, and here.) Thomas Aquinas argued that philosophically speaking, it seems that the human soul is subsistant without a body (though it will be incomplete), because it is has a function that it alone is capable of doing (it is also not dependant on the body to do it) - rational inference, reasoning.