we suppose men to know, though no one has explained their nature, and we
erroneously maintain them to be the letters or elements of the whole,
although they cannot reasonably be compared even to syllables or first
compounds. I am not now speaking of the first principles of things,
because I cannot discover them by our present mode of enquiry. But as I
observed the rule of probability at first, I will begin anew, seeking by
the grace of God to observe it still.

In our former discussion I distinguished two kinds of being--the unchanging
or invisible, and the visible or changing. But now a third kind is
required, which I shall call the receptacle or nurse of generation. There
is a difficulty in arriving at an exact notion of this third kind, because
the four elements themselves are of inexact natures and easily pass into
one another, and are too transient to be detained by any one name;
wherefore we are compelled to speak of water or fire, not as substances,
but as qualities. They may be compared to images made of gold, which are
continually assuming new forms. Somebody asks what they are; if you do not
know, the safest answer is to reply that they are gold. In like manner
there is a universal nature out of which all things are made, and which is
like none of them; but they enter into and pass out of her, and are made
after patterns of the true in a wonderful and inexplicable manner. The
containing principle may be likened to a mother, the source or spring to a
father, the intermediate nature to a child; and we may also remark that the
matter which receives every variety of form must be formless, like the
inodorous liquids which are prepared to receive scents, or the smooth and
soft materials on which figures are impressed. In the same way space or
matter is neither earth nor fire nor air nor water, but an invisible and
formless being which receives all things, and in an incomprehensible manner
partakes of the intelligible. But we may say, speaking generally, that
fire is that part of this nature which is inflamed, water that which is