science until alchemy was becoming decadent.  It is not surprising, therefore, that the alchemists—­these men who wished to probe Nature’s hidden mysteries—­should reason from above to below; indeed, unless they had started de novo—­as babes knowing nothing,—­there was no other course open to them.  And that they did adopt the obvious course is all that my former thesis amounts to.  In passing, it is interesting to note that a sixteenth-century alchemist, who had exceptional opportunities and leisure to study the works of the old masters of alchemy, seems to have come to a similar conclusion as to the nature of their reasoning.  He 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,