Q : ...the superior energetic essence is able to express itself in a physical form: why?
A : I should start discussing the Work of consecration of the matter. I think that, for reason of space, this is impossible in a mailing list.
I will only say that the spiritual essence ‘wishes' (!) to make the (decayed) matter relive, bringing it back to its original state. By doing so it recomposes the Harmony of the spiritual planes.
Q : ... according to which principles does this energy ‘decide' which form to take?
A : The characteristic of any inferior substance (denser because it undergoes a slower energetic frequency) when it is approached by a superior substance (for speed and vibration) is to become dissonant (conflicting). Therefore the ‘inferior substance' always puts up resistance to a greater simile (be it spirit, soul or conscience). In order to solve this problem (without breaking anything) it is necessary to create between them a kind of compensation room (the Bridge of conscience), which slowly reduces most of the conflict between the ‘two different similarities' (see duality).
From this it is easy to presume that the ‘form' under which an energetic drive like the spiritual one can appear (materialize by embodying), is strongly influenced by the resistance put by the physical substance.
Amalgamating all the diversities that put up resistance is a task of the Ego (intelligent activity) also called superior Self. In order to make its action more prompt and efficient, it is necessary that the personality (physical conscience) as well decides to ‘build' its own part of the Bridge that connects the ‘two realities'.
Q : How, when and most of all why is it necessary to ‘retire' from this ‘form'?
A : I suggest you read the Treaty: Morte, la Grande Avventura (Death, the Great Adventure, Note of the Translator), which you will find on the website.
Q : Can the same spiritual essence (soul) have several separated physical manifestations at the same time?
A : No.
Q : You say that ‘...physical expressions are nothing but the final link (each link is a different dimension) of evolving life, generating all the different forms of existence'. Aren't there any lower dimensions of existence?
A : Under ‘our universe', or more realistically, under what we can hardly perceive, there are other universes.
We know the dimension of the ‘extremely big' called macrocosm and that of the ‘extremely small' called microcosm .
But these are only the outlines of human existence, all determined by the ‘time factor'. By looking beyond, where time is not decisive or is completely absent, we would find universes greater than our macrocosm and smaller than our microcosm. The ‘above and under' though, are not only conventions of the physical reason, ruled by a two-dimensional thought. In actual fact it would be more appropriate to talk about ‘ in and out '.
When a Disciple starts thinking about the dimension perceived by the physical sense in terms of ‘in and out', this new way of thinking (based on the concept of space) makes it easier for him to ‘visualize' the idea of multi-dimension.
The concept of multi-dimension is not in or out, nor above neither under what the senses of the physical body perceive. Its characteristic is what ‘crosses' the various dimensions (inner spaces). In other words, in reality several planes place themselves one inside the other, crossing each other both longitudinally and transversally. It all happens ‘simultaneously' (law of synchronicity).
The spiritual vision is able to observe inside and through several dimensions at the same time. This gives an idea of the point of view of a Master.
Q : It is a mystery to me what: ‘getting closer to the living teaching' means.
A : What is ‘brought back' through ancient memories are often dreams. What is written is a ‘dead letter'. Only the Power of the word (prerogative of the Initiate) keeps and transmits, at least partly, the vitality ( Fire, Agni ) of the Idea; this is the esoteric meaning of the Mouth-Ear transmission.
But the living teaching is what we can receive from the first occult Master which is the superior Self. Indeed, the voice in the silence that ‘instructs' the reason of the Aspirant belongs to the Ego; this voice leads him on the Threshold of the Master.
I hope that you find these ideas useful.
Fraternally 
