writes: "The Sages... after having
conceived in their minds a Divine idea of the relations of the whole
universe... selected from among the rest a certain substance, from which
they sought to elicit the elements, to separate and purify them,
and then again put them together in a manner suggested by a keen and
profound observation of Nature."(1c)

(1a) _op cit_., pp,. 65 and 110, _cf_. p. 154.

(1b) _Vide_ a rather frivolous review of my _Alchemy: Ancient and
Modern_ in _The Outlook_ for 14th January 1911.

(1c) EDWARD KELLY: _The Humid Path_. (See _The Alchemical Writings_ of
EDWARD KELLY, edited by A. E. WAITE, 1893, pp. 59-60.)

In describing the realm of spirit as _ex hypothesi_ known, that of
Nature unknown, to the alchemists, I have made one important omission,
and that, if I may use the name of a science to denominate a complex of
crude facts, is the realm of physiology, which, falling within that of
Nature, must yet be classed as _ex hypothesi_ known. But to elucidate
this point some further considerations are necessary touching the
general nature of knowledge. Now, facts may be roughly classed,
according to their obviousness and frequency of occurrence, into four
groups. There are, first of all, facts which are so obvious, to put
it paradoxically, that they escape notice; and these facts are the
commonest and most frequent in their occurrence. I think it is Mr
CHESTERTON who has said that, looking at a forest one cannot see the
trees because of the forest; and, in _The Innocence of Father Brown_, he
has a good story ("The Invisible Man") illustrating the point, in which
a man renders himself invisible by dressing up in a postman's uniform.
At any rate, we know that when a phenomenon becomes persistent it tends
to escape observation; thus, continuous motion can only be appreciated
with reference to a stationary body, and a noise, continually repeated,
becomes at last inaudible. The tendency of often-repeated actions to
become habitual, and at last automatic, that is to say, carried
out without consciousness, is a closely related phenomenon. We
can understand, therefore, why a knowledge of the existence of the
atmosphere, as distinct from the wind, came late in the history of
primitive man, as, also, many other curious gaps in his knowledge. In
the second group we may put those facts which are common, that is, of
frequent occurrence, and are classed as obvious. Such facts are accepted
at face-value by the