But, nature was to be followed with eyes closed save to one vision, and the vision was to be seen before the following began.
The alchemists' general conception of nature led them to assign to every substance a condition or state natural to it, and wherein alone it could be said to be as it was designed to be.

Each substance, they taught, could be caused to leave its natural state only by violent, or non-natural, means, and any substance which had been driven from its natural condition by violence was ready, and even eager, to return to the condition consonant with its nature.
Thus Norton, in his _Ordinal of Alchemy_, says: "Metals are generated in the earth, for above ground they are subject to rust; hence above ground is the place of corruption of metals, and of their gradual destruction.

The cause which we assign to this fact is that above ground they are not in their proper element, and an unnatural position is destructive to natural objects, as we see, for instance, that fishes die when they are taken out of the water; and as it is natural for men, beasts, and birds to live in the air, so stones and metals are naturally generated under the earth." In his _New Pearl of Great Price_ (16th century), Bonus says:--"The object of Nature in all things is to introduce into each substance the form which properly belongs to it; and this is also the design of our Art." This view assumed the knowledge of the natural conditions of the substances wherewith experiments were performed.

It supposed that man could act as a guide, to bring back to its natural condition a substance which had been removed from that condition, either by violent processes of nature, or by man's device.

The alchemist regarded himself as an arbiter in questions concerning the natural condition of each substance he dealt with.