further and further back the unanalyzable residuum of Nature, but, however
far back, an ultimate unanalyzable residuum there must always be; and when
physical science brings us to this point it hands us over to the guidance
of psychological investigation just as in the Divina Commedia Virgil
transfers Dante to the guidance of Beatrice for the study of the higher
realms. Various rates of rapidity of motion in this primary ether,
producing various numerical combinations of positively and negatively
electrified particles, result in the formation of what we know as the
different chemical elements, and thus explains the phenomena of their
combining quantities, the law by which they join together to form new
substances only in certain exact numerical ratios. From the first movement
in the primary ether to solid substances, such as wood or iron or our own
flesh, is thus a series of vibrations in a succession of mediums, each
denser than the preceding one out of which it was concreted and from which
it receives the vibratory impulse. This is in effect what physical science
has to tell us. But to get further back we must look into the world of the
invisible, and it is here that psychological study comes to our aid. We
cannot, however, study the invisible side of Nature by working from the
outside and so at this point of our studies we find the use of the
time-honored teaching regarding the parallelism between the Macrocosm and
the Microcosm. If the Microcosm is the reproduction in ourselves of the
same principles as exist in the Macrocosm or universe in which we have our
being, then by investigating ourselves we shall learn the nature of the
corresponding invisible principles in our environment. Here, then, is the
application of the dictum of the ancient philosophy, "Know Thyself." It
means that the only place where we can study the principles of the
invisible side of Nature is in ourselves; and when we know them there we
can transfer them to the larger world around us.

In the concluding chapters of my "Edinburgh Lectures on Mental Science" I