Such terms as hardness, softness, coldness, toughness, and the like, are employed for the purpose of bringing together into one point of view different things which are alike in, at least, one respect. Hard things may differ in size, weight, shape, colour, texture, &c. A soft thing may weigh the same as a hard thing; both may have the same colour or the same size, or be at the same temperature, and so on. By classing together various things as hard or soft, or smooth or rough, we eliminate (for the time) all the properties wherein the things differ, and regard them only as having one property in common. The words hardness, softness, &c., are useful class-marks.
Similarly the alchemical Elements and Principles were useful class-marks.
We must not suppose that when the alchemists spoke of certain things as formed from, or by the union of, the same Elements or the same Principles, they meant that these things contained a common substance. Their Elements and Principles were not thought of as substances, at least not in the modern meaning of the expression, a substance; they were qualities only.
If we think of the alchemical elements earth, air, fire, and water, as general expressions of what seemed to the alchemists the most important properties of all substances, we may be able to attach some kind of meaning to the sayings of Basil Valentine, which I have quoted. For instance, when that alchemist tells us, "Fire is the most passive of all elements, and resembles a chariot; when it is drawn, it moves; when it is not drawn, it stands still"—we may suppose he meant to express the fact that a vast number of substances can be burnt, and that combustion does not begin of itself, but requires an external agency to start it.
Unfortunately, most of the terms which the alchemists used to designate their Elements and Principles are terms which are now employed to designate specific substances. The word fire is still employed rather as a quality of many things under special conditions, than as a specific substance; but earth, water, air, salt, sulphur, and mercury, are to-day the names applied to certain groups of properties, each of which is different from all other groups of properties, and is, therefore, called, in ordinary speech, a definite kind of matter.
As knowledge became more accurate and more concentrated, the words sulphur, salt, mercury, &c., began to be applied to distinct substances, and as these terms were still employed in their alchemical sense as compendious expressions for certain qualities common to great classes of substances, much confusion arose. Kunckel, the discoverer of phosphorus, who lived between 1630 and 1702, complained of the alchemists' habit of giving different names to the same substance, and the same name to different substances. "The sulphur of one," he says, "is not the sulphur of another, to the great injury of science. To that one replies that everyone is perfectly free to baptise his infant as he pleases. Granted. You may if you like call an ass an ox, but you will never make anyone believe that your ox is an ass." Boyle is very severe on the vague and loose use of words practised by so many writers of his time. 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. Let us illustrate the matter by supposing a glass of water to be set in the middle of a table, round the margin of which are placed little heaps of salt, and of powders of different colours. If the water be poured out, it will run all over the table in divergent rivulets, and will become salt where it touches the salt, red where it touches the red powder, and so on. The water does not change the 'places,' but the several 'places' differentiate the water.[4] In the same way, the seed which is the product of the four Elements is projected in all directions from the earth-centre, and produces different things, according to the quality of the different places. Thus, while the seed of all things is one, it is made to generate a great variety of things.... So long as Nature's seed remains in the centre it can indifferently produce a tree or a metal, a herb or a stone, and in like manner, according to the purity of the place, it will produce what is less or more pure."