The Solfatara itself is a trough surrounded by hilly mounds; its smooth, saucepan-like bottom, covered with whitish pumice-sand, is pitted with craters containing violently boiling and fuming mud - the so-called fango, famous for its healing properties. All around sulphurous fumes issue from crevices in the rocks, and in one special place the Solfatara reveals its subterranean activity by the emergence of fine, many-coloured sand, which oozes up like boiling liquid from the depths below. The whole region gives the impression of being in a state of labile balance. How true this is becomes apparent if one drops pieces of burning paper here and there on the ground: immediately a cloud of smoke and steam rises. The effect is even more intense if a burning torch is moved about over one of the boiling fango holes. Then the deep answers instantly with an extraordinary intensification of the boiling process. The hot mud seems to be thrown into violent turmoil, emitting thick clouds of steam, which soon entirely envelop the spectator near the edge.

³ In a later chapter we shall have opportunity to determine what distinguishes Air from Fire, on the one hand, and Water from Earth on the other.

In a science based on the Goethean method of contemplating the world of the senses, concepts such as 'mass in rest' and 'mass in motion' lack any scientific meaning (though for another reason than in the theory of Relativity). For in a science of this kind the universe - in the sense propounded lately by Professor Whitehead and others - appears as one integrated whole, whose parts must never be considered as independent entities unrelated to the whole. Seen thus, there is no mass in the universe of which one could say with truth that it is ever in a state of rest. Nor is there any condition of movement which could be rightly characterized by the attributes 'uniform' and 'straight line' in the sense of Newton's first law. This does not mean that such conditions never occur in our field of observation. But as such they have significance only in relation to our immediate surroundings as a system of reference. Even within such limits these conditions are not of a kind that would allow us to consider them as the basis of a scientific world-picture. For as such they occur naturally only as ultimate, never as primeval conditions. All masses are originally in a state of curvilinear movement whose rates change continuously. To picture a mass as being in a state of rest, or of uniform motion in a straight line, as the result of no force acting on it, and to picture it undergoing a change in the rate and direction of its motion as the result of some outer force working on it, is a sheer abstraction. In so far as mass appears in our field of observation as being in relative rest or motion of the kind described, this is always the effect of some secondary dynamic cause.

The first systematic teaching about the four elementary constituents of nature, as they were experienced by man of old, was given by Empedocles in the fifth century B.C. It was elaborated by Aristotle. In this form it was handed down and served to guide natural observation through more than a thousand years up to the time of van Helmont. From our earlier descriptions of the changes in man's consciousness it is clear that the four terms, 'earth', 'water', 'air', 'fire', must have meant something different in former times. So 'water' did not signify merely the physical substance which modern chemistry defines by the formula H₂O; nor was 'air' the mixture of gases characteristic of the earth's atmosphere. Man in those days, on account of his particular relationship with nature, was impressed in the first place by the various dynamic conditions, four in number, which he found prevailing both in his natural surroundings and in his own organism. With his elementary concepts he tried to express, therefore, the four basic conditions which he thus experienced. He saw physical substances as being carried up and down between these conditions.

In modern science the earth is regarded as a mineral body whereon the manifold forms of nature appear as mere additions, arising more or less by chance; one can very well imagine them absent without this having any essential influence on the earth's status in the universe. The truth is quite different. For the earth, with everything that exists on it, forms a single whole, just as each separate organism is in its own way a whole.

We said earlier in this chapter that a science which aspires to a spiritual understanding of the physical happenings in nature must give up the idea that inertness and weight are absolute properties of matter. We were able at once to tackle the question of inertness by bringing to our immediate observation matter in the state of diminished inertness, or, as we proposed to say, of alertness. We are now in a position to go into the other question, that of weight or gravity. Just as we found inertness to have its counterpart in alertness, both being existing conditions of matter, so we shall now find in addition to the force of gravity another force which is the exact opposite of it, and to which therefore we can give no better name than 'levity'.

The scientific mind is at first inclined to see in this phenomenon the mechanical effect of reduced air-pressure, due to the higher temperatures above the surface of the boiling mud, though doubts are raised by the unusual intensity of the reaction. The feeling that the physical explanation is inadequate is strengthened when the vapours have thinned out and one is surprised to see that every crack and cranny in the Solfatara, right up to the top of the trough, shows signs of increased activity. Certainly, this cannot be accounted for by a cause-and-effect nexus of the kind found in the realm of mechanical causation, where an effect is propagated from point to point and the total effect is the sum of a number of partial effects. It looks rather as if the impulse applied in one spot had called for a major impulse which was now acting on the Solfatara as a whole.

⁴ It is this apparent uni-polarity of gravity which has given Professor Einstein so much trouble in his endeavour to create a purely gravitational world-picture with bipolar electricity and magnetism fitting into it mathematically.

If we wish to think with the course of the universe and not against it, we must not start our considerations with the state of (relative) rest or uniform motion in a straight line and derive our definition of force from the assumption that there is a primary 'force-free' state which is altered under the action of some force, but we must arrange our definitions in such a way that they end up with this state. Thus Newton's first law, for instance, would have to be restated somewhat as follows: No physical body is ever in a state of rest or uniform motion in a straight line, unless its natural condition is interfered with by the particular action of some force.

At first sight some relationship seems to exist between the concept 'element' in this older sense and the modern view of the different states of material aggregation, solid, liquid, aeriform. There is, however, nothing in this modern view that would correspond to the element Fire. For heat in the sense of physical science is an immaterial energy which creates certain conditions in the three material states, but from these three to heat there is no transition corresponding to the transitions between themselves. Heat, therefore, does not rank as a fourth condition by the side of the solid, liquid and aeriform states, in the way that Fire ranks in the older conception by the side of Earth, Water and Air.