During many stays on the Earth a man had to use his skills and characteristics maximally during rough gusty and life- conditions to survive. The soul, but also the spiritual germ, had to strain more, to create more warmth to penetrate through thick material cloak- the body and through it they could act on the their surrounding and make it more perfect. The spiritual germ activated in colder and rougher environment. It had to get used to control its body similar as a man, who has to get used to work in thick rubber- gloves.
An idea may strike you why the development of the soul in ethereal matter is not sufficient for the spirit-germ to return to the Paradise. Just for the reason that the ethereal world was not "harsh", cold and material enough to awake the slumbering qualities of the spirit germ to the maximum. The spirit-germ could enter the Earth, coarse matter only after its soul had developed to be able to master its heavy material body by means of the soul. The spirit-germ itself, without the soul, would not even move with the body nor would keep inside it according to the Law of the Attraction of Homogeneous Species. The immense difference of its nature when compared with matter would cast it out.
Nor the soul is a homogeneous mediator for the material body. It is too fine to be able to maintain itself inside the body. Therefore, the little elemental beings adapted to this activity produce out of medium gross matter the astral body of man. It forms a link between the ethereal soul, because it is slightly coarser and the gross material body because it is finer. After earthly death of man the astral body comes out of the material body and decomposes into original elements in the astral world. However, it has longer durability than the material body. Since it is of the human appearance some "sensitive men" are capable to see it with their ethereal sight.
During its last residence on earth occurring for each man in different periods the spirit germ develops into the perfect personality bearing either the feminine or the masculine appearance. After death the mature spirit goes home - to the Paradise. At each plane which he crosses - in the World of Ethereal Matter and in the Realm of Animistic Substantiality - there he leaves his cloaks which get burned one after the other under the strong radiation of the matured spirit.
From what comes the strong radiation of a spirit that burns the psychical cloaks? When the improved spirit gets the human appearance, the man has to develop the psychical and spiritual power, too. That becomes more strong through fighting with the difficulties and also through realising spiritual truths in everyday life. Who reads them only and does not put them in real life, will not get the spiritual power, the strong radiation that destroys the psychical cloaks.
The return of the spirit to the Spiritual Realm, to the Paradise, is connected with the further development under control of the spirit guide who leads the spirit to the right place. Under influence of the Law of Reciprocal Action the spirit-germ who was initially unconscious returns as the conscious spirit to the place from which he set out because everything must be closed in the cycle. This happening is depicted in the parable of "the lost son".