In _The Sceptical Chymist_ (published 1678-9) he says: "If judicious men, skilled in chymical affairs, shall once agree to write clearly and plainly of them, and thereby keep men from being stunned, as it were, or imposed upon by dark and empty words; it is to be hoped that these [other] men finding, that they can no longer write impertinently and absurdly, without being laughed at for doing so, will be reduced either to write nothing, or books that may teach us something, and not rob men, as formerly, of invaluable time; and so ceasing to trouble the world with riddles or impertinences, we shall either by their books receive an advantage, or by their silence escape an inconvenience." Most of the alchemists taught that the elements produced what they called _seed_, by their mutual reactions, and the principles matured this seed and brought it to perfection.

They supposed that each class, or kind, of things had its own seed, and that to obtain the seed was to have the power of producing the things which sprung from that seed.
Some of them, however, asserted that all things come from a common seed, and that the nature of the products of this seed is conditioned by the circumstances under which it is caused to develop.
Thus Michael Sendivogius writes as follows in _The New Chemical Light, drawn from the fountain of Nature and of Manual Experience_ (17th century):-- "Wherever there is seed, Nature will work through it, whether it be good or bad." "The four Elements, by their continued action, project a constant supply of seed to the centre of the earth, where it is digested, and whence it proceeds again in generative motions.

Now the centre of the earth is a certain void place where nothing is at rest, and upon the margin or circumference of this centre the four Elements project their qualities....

The magnetic force of our earth-centre attracts to itself as much as is needed of the cognate seminal substance, while that which cannot be used for vital generation is thrust forth in the shape of stones and other rubbish.

This is the fountain-head of all things terrestrial.