280. Because living beings mounting the steps do not have exactly the same forms, there are what we call "species". In order to understand the basic cause why living beings on the evolutionary ladder appear as different species we must realize that evolution itself is supported by the individual's perception of experiences and that this perception, in its cosmic analysis, is synonymous with the strongest release of the creative factor in the individual's bodily structure. As will be explained later and has already been touched upon, the living being is an eternal reality with an ever-changing bodily structure which causes it to experience its own existence in the form of "single lives". The individual's whole bodily structure consists of seven different bodies corresponding to life's seven basic energies. It is the seventh of these bodies which constitutes the individual's true eternal body, while the six others should be regarded actually as constituting the organs in that body. As an individual is able to experience his eternal existence only by these said organs of his eternal body and these again are material realities, and consequently, like all other material phenomena are subject to ageing and wear or what is called by some people the "tooth of time", then these organs or bodies must be renewed continuously. This renewal process does not come about simultaneously for all the bodies, but takes place in such a way that the individual always has one of his bodies in full development while the others, in relation to the latter, are found in a gradually increasing or decreasing state of usefulness. The individual thus experiences life mainly through only one of his bodies at a time and each body provides its own special sense horizon. And so he meets with his own eternal existence in the form of six different sense horizons, which means that every living being's eternal existence is identical with an ever-changing experience of six different forms of single lives.