II

Our modern idea that science embraces all kinds of knowledge is, as

I have mentioned before, a curious reversion to the Greeks. In spite

of the fact that they formulated the great deductive laws of physics,

such as cause and effect, conservation of matter, etc., and developed

an extraordinarily fruitful science of geometry, they remained

indifferent to the experimental method. They developed almost no

apparatus for experimentation, established no standards of measurement,

and their arithmetical symbols were so awkward that only the simplest

calculations could be made. They never succeeded in disentangling

subjective and objective ideas. Plato could anticipate the modern

conception of natural law in his aphorism that God geometrises, but

at the same time he vaguely identified the human soul with the stars

and endued the universe with life. Democritus pictured the world as an

aggregation of atoms, differing only in size, shape, and motion; yet

he also tacitly ascribed to them a will or desire to move which was

only less pronounced than in those finer particles which constituted

the souls of men. Also the four classic elements,--earth, water, air,

and fire,--which combined in different proportions to form all material

bodies, were actuated by the animistic principle that each element

sought its own place. One could multiply these examples of classical

thought which confused mechanical forces with the vital attributes of

will and desire.

The failure of the Greeks to develop an objective and experimental

method was intensified by the domination of the Christian religion

during the Middle Ages. The emphasis of thought was placed on the

problems of human character. At a time when men were taught that our

environment was a trap set by the powers of evil to allure our souls to

eternal damnation, there could be little stimulus to study the laws of

nature or to apply them to increase our interest in a temporal life. It

is customary for historians to condemn the Church for having crushed

science, but no concerted opposition was necessary in a society which

saw no advantage in gathering its fruits. It was an axiom that truth

was the direct consequence of intuition and revelation, that God had

revealed in the Bible, and through His living Church, all the knowledge

necessary for man’s guidance in a transitory state. To neglect such a

certainty for the perceptions of our fallible and sinful senses, and to

construct a world from them according to our reason, would be to fall

into the sin of the pride of the intellect. Furthermore, in a society

small in numbers and in area, where the greater number were believed to

have been created to minister to the comfort of the few, little need

was felt for mechanical power and industry. The only science which

seemed to be worth cultivating was one which was believed to foretell

human events and to affect our spiritual life.

It had been generally accepted from ancient times that the stars

influenced our lives and foretold the future. Such knowledge was

eagerly sought by a society which was principally concerned with

religion and was, at the same time, a prey to superstitious fear.

It is not surprising that astrology was seriously cultivated. If we

grant the postulate that the stars do affect us, then we must admit

that astrology was a true science. The positions and the motions of

the planets and stars were observed and recorded as accurately as

possible, and deductions were made according to rules and laws believed

to have been verified by experience. Nor does it seem to me much more

credulous to believe that our character is determined by the relative

positions of the planets, than to assume, as do Mr. Watson and the

modern behaviourists, that our thoughts are caused by the relative

positions and motions of the material atoms which happen to compose

the substance of our brains. The astrologists had, at least, the great

advantage of dealing with real bodies which we can observe, while these

psychologists have for their use only the hypothetical and machine-made

atoms of the chemist which they can never hope to observe. There is

little to choose between the superstition that the planets foretell our

characters and the superstition that atoms constitute thought; both

lead to equally foolish and irrational practices. And there is the

less excuse for the psychologist, since he has had the benefit of a

longer past experience than had the astrologer to convince him of the

futility of identifying mind and matter.

The only other science which aroused popular interest was alchemy. The

basis of this subject was the postulate that all matter was composed

of the four elements combined in various proportions. By the use

of chemical reagents, the combinations of these elements could be

altered and a given substance be thus changed into another. Alchemy

is generally associated with the attempt to transmute metals and, in

particular, to change lead into gold, because the natural cupidity

of their patrons made it advisable for the alchemists to hold that

prospect before them in order to obtain a livelihood. In principle,

alchemy is but little different from modern chemistry. Our most recent

theory still holds that the difference between lead and gold is due

only to the numerical relations of a single element, the electron. The

difference between chemistry and alchemy does not lie in either their

fundamental hypotheses or their methods, but in our vastly superior

technique of experimentation and accumulated knowledge. The nature of

the modern electronic atom is essentially as fictitious as was the

nature of the mediæval elements.

Besides exciting the hope of wealth, alchemy was important as an aid

to health and longevity. Since health required that the four elements

of the body should be preserved in their proper balance, illness, and

even death, were but the temporary or permanent loss of their right

proportions. Alchemists, convinced of this truth, were led to seek for

a sovereign substance, the philosopher’s stone, which would have the

power to restore this disturbed balance and give to its fortunate owner

permanent health and life.

It is a mistake to suppose that the Church oppressed these

sciences--many of its most orthodox fathers and saints eagerly studied

them. The abuses due to the rampant charlatanry of many of their

practitioners were repressed, but their serious doctrines were fused

into the religion of the time much as, in our day, the clergy have

tried to harmonise Christianity and biological evolution. In fact, as

we shall see, the most determined opposition which the new Copernican

theory of the solar system had to overcome was the fusion of Christian

dogma with Aristotelian astrology and alchemy.

It was natural that the first fruits of the new science of the

Renaissance should have been in astronomy and mechanics. The

accumulated observations of the astrologers had vastly increased the

complexity of the Ptolemaic system, and the discrepancies between

the observed and calculated positions of the planets had become

glaringly evident. When the great treatise of Copernicus was finally

published as he lay on his death-bed, it is altogether probable that

no one suspected that it marked the beginning of a new philosophy. He

had merely proved that the calculations of astronomers were greatly

simplified by assuming that the sun, instead of the earth, was the

fixed centre of the solar system, and that the earth and other planets

revolved about it in circular orbits. It must remain a mooted question

whether Copernicus believed that his discovery was only a mathematical

device; his book states explicitly that he, as a Catholic, still

subscribed to the belief that the earth was actually the fixed centre

of the universe as the Church and the Aristotelians both taught to be

a necessary article of faith. At all events, it was not until Galileo

some sixty years later invented the telescope and turned it on the

heavens, that men saw the significance of the discovery. The eye of

the telescope penetrated the depths of the solar system. It proved

that the planets were not pure celestial matter but were mere masses

like the earth. Their brilliance was not a divine fire but ordinary

sunlight reflected from their dull surfaces; they, like the earth,

were inanimate bodies revolving about the sun and the Copernican system

became a fact instead of a mathematic device. It is not extravagant to

assert that, with the acceptance of Copernican astronomy, the whole

mediæval conception of nature gave place to a reliance on experimental

evidence.

The work of Galileo in founding the science of mechanics was fatal to

the mysticism of the contemporary alchemists. Instead of the elements

with their natural places, their likes and dislikes, their hierarchy of

nobility, and their subserviency to planetary influences, he laid down

the universal principle that all natural actions were due to mechanical

forces whose only function was to alter the motions of bodies and whose

amount was measurable in mathematical symbols. His significant work for

us was an uncompromising war waged against the scientific dogmatism

of the Aristotelians on the clear-cut issue that knowledge of the

objective world could be obtained only by experimental evidence, and

not by subjective preconceptions. Understood rightly, he had reinstated

the Platonic dualism of two worlds, one of matter, and the other of the

mind or spirit.

It is significant that during Galileo’s lifetime, so swift was the

movement, Descartes saw the trend of the new science and its inevitable

effect on philosophy and religion. In his _Système du Monde_, he

pictured a universe of matter and motion and nothing else,--a

machine. From matter he tried to strip every sensible attribute

except extension, or its mere geometrical position and extent. All

phenomena became for him merely phases of motion. With the courage

of his conviction, he even tried to imagine plants and animals to be

mechanically acting automata. One thing only he could not include in

this mechanism,--and that was _thought and consciousness_.

The cosmogony of Descartes has long since crumbled to dust, but the

gap he made between the subjective and objective worlds has never been

closed in spite of incessant later attempts. And these early creators

of science, as something distinct from humanism, were quite conscious

that they were engaged in a revolution which could end only with the

overthrow of the dogmatic science of the Middle Ages, sheltered by the

authority of Aristotle and the Bible. Galileo, Descartes, Pascal, and

Bacon all declared explicitly that the old order must pass. From their

day to ours, we have more and more regarded the universe as a machine,

a combination of inert matter and moving forces, acting not as we may

desire, but according to invariable laws which we have personified as

Nature. Man was left, by the physicists, as a unique outsider who could

interpret this machine in terms of his sensations and mind, but could

neither alter nor avoid its fateful operation.

Only one step further was needed to identify all science with mechanics

and to compress the scientific method within the limits imposed by

mechanical laws. This fundamental principle was Newton’s discovery

of the universal attraction of matter. According to this law, a

single kind of force, depending only on the amount of matter and the

distance between bodies, operated to hold the stars in their paths

and to cause all the chemical and physical activities of atoms. With

its discovery, the mechanistic theory was complete and dominant,

and science had, in principle, gone as far as it can ever go. But,

what is even more important, Newton grasped in his early years the

fact that the scientific method is limited to the experimental

investigation of objective phenomena, those which can be classified,

measured geometrically, and formulated in laws which predict future

events. He held with absolute consistency and restraint that what is

once accomplished by this method is permanent. The experimental laws

of gravitation, of the pressure of gases, and all others of like

nature, are true within the limits of accuracy of our observation

and measurement. If these improve, such laws do not fail, their

mathematical expression is merely made more precise. They belong to the

permanent acquisitions of the mind.