In our planetary system the number of the invisible planes is seven.[61] Each of them in turn supplies the soul with a form; thus, when evolution--which in its second phase successively dematerialises matter, _i.e._, disassociates the atoms from their combinations, beginning with the denser ones--has dissolved the physical plane, the human soul will utilise, as its normal body, a finer one which it is at present using as a link between the mental and the physical bodies. Before this dissolution is effected, however, human beings will have developed, to some extent, several finer bodies, already existing, though hitherto not completely organised. The first of these bodies, the astral--a very inappropriate name, though here used because it is so well known--is a copy, more or less, of the physical form in its general aspect; the resemblance and clearness of the features are pronounced in proportion to the intellectual development of the person, for thought-vibration has great influence over the building up of the centres of force and of sensation in this body.[62] The second is an even finer aggregate, composed of mental substance and assuming, during incarnation, the form of a smaller or larger ovoid--the causal body--surrounding the physical form.[63] At its centre, and plunged in the astral body during incarnation, is another kind of ovoid not so large and composed of denser substance--the mental body.[64] Above these states of matter, at the present stage there appears no form to the consciousness of human beings, though perfect seers can perceive, within the causal body, still higher grades of matter, which will only subsequently become centres of self-consciousness. During incarnation, the soul, in the majority of men, is clearly conscious of itself and of its surroundings only when it is functioning through the nervous system (the brain); when it leaves the denser body, during sleep, its consciousness is in the astral body, and there it thinks,[65] but without being conscious of what is taking place around it. After disincarnation, it generally becomes highly conscious in its astral body, where it passes its purgatorial life; and this latter endures until the soul leaves the astral body. As soon as the latter is thrown off, consciousness centres in the mental body; this is the period of _Devachan_ or Heaven. When the mental body is put off, paradise is at an end, and the soul, sheathed only in the causal body, finds itself on a very lofty plane, but here, consciousness is vague, when we are dealing with a man of average development. Instead of laying aside this garment, as so far it has done with the rest, it recommences, after the lapse of a certain time, another descent into the matter of the lower planes and a new incarnation begins.