If you fold a piece of paper into the form of a dart it will fly through the air by the law of the form which you have given it.

Again, if you take the same bit of paper and fold it into the shape of a boat it will float on water by the law of the new form that you have given it.

The thing formed will act in accordance with the form given it, and the same paper can be folded into different forms; but if there were no paper you could put it into any shape at all.
The dart and the boat are both real so long as you retain the paper in either of those shapes; but this does not alter the fact that you can change the shapes, though your power to do so depends on the existence of the paper.

This is a rough analogy of the relation between ultimate substance and particular forms, and shows us that neither substance nor shape is an illusion; both are essential to the manifestation of Spirit, only by the nature of the Creative Process the Spirit has power to determine what shape substance shall take at any particular time.
Accordingly we find the great Law that, as Spirit is the Alpha of the Creative Process, so solid material Form is its Omega; in other words the Creative Series is incomplete until solid material form is reached.
Anything short of this is a condition of incompleteness, and therefore the enlightened souls who have passed over in possession of both sides of their mentality will realize that their condition, however beatific, is still one of incompleteness; and that what is wanted for completion is expression through a material body.

This, then, is the direction in which such souls would use their powers of initiative and selection as being the true line of evolution--in a word they would realize that the principle of Creative Progression, when it reaches the level of fully developed mental man, necessarily implies the Resurrection of the Body, and that anything short of this would be retrogression and not progress.
At the same time persons who had passed over with this knowledge would never suppose that Resurrection meant merely the resuscitation of the old body under the old conditions; for they would see that the same inherent law which makes expression in concrete substance the ultimate of the creative series also makes this ultimate form depend on the originating movement of the spirit which produces it, and therefore that, although _some_ concrete form is essential for complete manifestation, and is a substantial reality so long as it is maintained, yet the maintaining of the particular form is entirely dependent on the action of the spirit of which the form is the external clothing.