history> newtonThis is the third of three pages in this history section - Anaximander, Atomism and Newton.
the scientific revolution
As with Ionian Greece, social changes helped give birth to the
scientific attitude. Medieval society was feudal and inward-looking,
the Catholic Church the safe-keeper of ideas. But with the Renaissance,
first in Italy, and then later in northern Europe, the power shifted to
cities reliant on trade and technology. Belief in authority was
replaced by a more questioning outlook.
And in the machines and instruments of the age - the clock, the printing press, the telescope, the cannon - lay the obvious inspiration for a more machine-like and instrumental view of the world. But what really sparked a revolution was the rediscovery of the full breadth of ancient philosophy, especially the simplicities of atomism.
Between the fall of Rome and the rise of Europe, Greek philosophy had lived on in Arab scholarship. Books preserved in middle eastern libraries reached Europe first as a steady trickle through the Moorish occupation of Spain, and then as a flood with those fleeing the sack of Constantinople in the mid-fourteenth century. The invention of the printing press meant that by the end of the fifteenth century some 10 million books were in circulation. And so a Christian world that had subsisted for so long on a thin gruel of bastardised Aristotelianism and theological debate found itself at a banquet of ideas.
There was also the will and wherewithal to test these ideas using the open communal method of scientific experiment. Philosophy depended on a subjective evaluation. Did a rational explanation seem plausible in the mind of a listener? But science measured these mental models against the real world. And with anybody being able to repeat an experiment to see if they got the same results, the testing of impressions became that much less personal and subjective, that much more impersonal and therefore objective.
The first great scientific shock was Copernicus’s discovery that the earth revolved around the sun. Among other things, this scuppered Aristotle’s argument that objects fell because the earth happened to be at the centre of the Universe. Kepler then found that the planets revolved not in circular but elliptic orbits. This contradicted the Aristotelian claim that the natural motion of the heavens would be perfect circles.
The surprises kept coming. Galileo turned a home-made telescope on the night sky and saw the moon was cratered. Saturn was misshapen by what turned out to be its rings. The sun was blemished by sun spots. Jupiter had its own four moons. Venus waxed and waned as it circled the sun. All this could only mean the earth was part of a solar system, a physical collection of large rocks around a ball of fire. The heavens were the same as the earth and obeyed the same rules. They could no longer claim a divine perfection. If a creating God existed, he was rapidly being pushed outside His own creation.
Encouraged to look more closely at the world about them, Renaissance scientists found that many things were not as they had imagined. Their ideas – shaped by the Medieval view of Aristotelian physics – had completely misled their impressions. For example, it was believed that heavier weights fall faster. Applying Aristotle’s teleological reasoning, they would feel more desire to move towards the centre of the earth. Yet also, because this desire was a constant property, the rate of descent would be constant as well.
Galileo, a particularly vigorous experimenter, was said to have tested the truth of this by dropping two weights, a 200 pound cannon ball and a half pound musket ball, off the Leaning Tower of Pisa. Whether or not this is legend, we can be sure the pair would have smacked the ground at exactly the same moment. As every school child now learns, even a feather and a cannonball would fall at the same rate if dropped together in a vacuum with no air to slow down the descent by friction.
Then to check if the rate of fall was constant, Galileo had the ingenious idea of slowing things down to an observable speed by rolling a bronze ball down a groove in a long plank. With a water clock he timed how long it took for the ball to reach various marks on the run. It turned out that falling objects did not travel at one rate but accelerated. From rest they moved faster and faster, their speed growing as a square of the distance. Again, the drag of friction eventually put a limit on the speed. But Galileo could see that in a completely frictionless world, a dropping body should just go on getting faster and faster.
And here matters got really exciting. Galileo imagined what would happen if he could build an infinitely-long frictionless rail at the end of his ramp. The ball would roll down, accelerating all the way, and then hit the flat bit. There it could not gain any further speed – but nor should it lose any. Without friction it now ought to keep rolling along at the same constant speed forever!
Aristotelian physics said bodies seek to be at rest and only move when made to. An unnatural motion, such as being propelled sideways through the sky like an arrow, required the continuing push of either bow or the air rushing in behind the arrow’s tail to prevent a momentary vacuum. While natural motions like rising and falling – or for the aether, circling – came from a material’s equally constant desire to reach its rightful destination. Once there, it would halt. But Galileo’s experiments were suggesting that objects were quite happy to be in motion. They would sail along of their own accord unless slowed by some external force like the drag of friction, or speeded up by the tug of some other kind of force like the pull of gravity.
This was the principle of inertia – the realisation that a mass will move at a constant rate unless accelerated or decelerated by an applied force. And it has huge consequences for our view of the world. To be at rest seems like such a natural, untroublesome state. It is simply to have existence at a location. A body’s absence of motion does not appear to demand a causal explanation.
But Galileo showed the reverse to be the case. To be crisply at rest now seemed so unlikely as to be just about impossible. A mass would have to become actively stopped, robbed of its motion and constrained to one place by a precisely opposed network of forces. And as Galileo pointed out, even then it would only be possible to know that the mass was stationary from the point of view of a particular observer, a particular frame of reference.
Galileo offered the example of being in the cabin of a ship. So long as the sea was calm, from inside you would not be able to tell whether you were tied up in harbour or pulling across the open sea. You might try various tests such as dropping objects or jumping up and down in the same spot. But the results would seem the same. Whether in port or at sea, weights dropped from the masthead would fall straight to the deck. The boat won’t run away from under you while you are poised mid-leap. Yet an observer with a spyglass on shore would see matters differently. The stone dropped from the mast of a moving boat would trace a forward arc as it fell. Your leap would go sideways as well as up and down. The observer can detect the constant momentum imparted by the passage of the ship as well as the acceleration downwards cause by the force of gravity.
As Einstein later coined it, all states of motion – or rest – are strictly relative to the observer. The ship itself is spinning with the earth, the earth wheeling with the solar system, the solar system tumbling with the stars and galaxies. So to be standing at absolute rest, to have zero motion, in terms of the whole of the rest of the Universe becomes something quite unimaginable. It is a state that might be approached perhaps. But true rest would have to be the ultimately unreachable limit of a dichotomy. (The other end of that relativistic dichotomy, of course, being Einstein’s upper boundary on motion – the speed of light.)
After Galileo came Newton. There were many other thinkers who were hastening science towards its atomistic, mechanical, vision of Reality such as Descartes, Gassendi, Boyle, Bacon and Hobbes. But it was Isaac Newton who actually completed what Galileo had begun.
In 1665 the threat of the plague
forced a 23-year-old Newton
his studies at Cambridge University and spend two years at home on the
farm. During this break, Newton made his discoveries in optics. Using a
prism and lens he showed that white light was a mix of colours
– an atomistic variety of corpuscles or particles. He also
invented the calculus as a way of modelling continuous change in the
world. And finally, inspired by atomist philosophy and a recently
acquired volume of Galileo's physics, he worked out the universal laws
of motion and gravity. Newton’s laws of motion are quite
simple but they demand
radical assumptions to be made about Reality. Newton's first law
restates Galileo’s principle of inertia then adds the crucial
fact that an already moving body will keep moving at the same rate in a
Galileo had wrongly believed a curving body like an orbiting planet would keep travelling in a curve. Newton showed instead that the inertial motions of masses and the dimensions of space are somehow directly connected – two faces of the same coin. In a “free” way, costing no effort, a mass could roll along the same straight path through space forever. But to also get a mass moving through either of the other two dimensions at the same time, as it must do if it wants to curve, spiral, rotate or otherwise alter course, requires an effort of some sort.
It is interesting to look at this from the point of view of the dimensions themselves. The motion of any mass travelling in an exact straight line becomes literally invisible to the other two dimensions. They cannot measure it. In a three dimensional realm, any two dimensions would form a plane and the third dimension would stick out at exact right angles. A straight-line perfectly aligned with this third dimension would only appear as a point-like cross-section in the other two dimension. So for them it would be a little like looking down a long tube. A mass might be moving in this pipe, but it would be impossible to tell whether it was advancing or retreating.
However as soon as the mass tried to deviate off course, intruding into the plane mapped out by the other two dimensions, then the point of intersection would be seen to move. The mass’s speed through their own share of the world would become obvious.
So here we have a peculiar thing. If we can speak of the forming of crisp dimensionality – crisp axes of description – as emerging from a system of mutual constraint, then we find there is a fundamental limit to how tightly the web of constraint can be drawn. An x and y-axis are formed by a dichotomous separation. Each becomes crisply defined in terms of what it is not. And then from these asymmetric limits set at exact right angles, it becomes possible to measure the position of every point on a plane. There don’t need to be any other axes of description. Between them, the x and y axis exclude all other dimensions from their world.
Or rather, they almost do. They certainly constrain any further impulse towards the expression of dimensionality to a “point”. But a point can conceal a suggestively asymmetric pair of alternatives. Either the points of a plane can harbour a further set of tiny curled-up dimensions – like the extra dimensions postulated in string theory, which being Planck-scale are so small they can’t be seen. Or the points mark an intersection with a fully extended third dimension that stands precisely end-on to the plane and can’t be seen for that reason.
So in a system formed of mutual constraint – where the parts are trying to separate themselves into crisp existence by ridding themselves of all that they recognise as “other” – each pair of dimensions could end up actually creating a crisply orthogonal third dimension. In dichotomising a vaguer state of space to create the crisply existent limits of an x and y-axis, all other visible directions would be squeezed out of existence. Which of course leaves as the only other possible extended dimension the straight line of a z-axis intersecting the plane at precisely right angles. In preventing all movements in the x and y direction, the z direction would now emerge as a dimension in which movements were crisply unconstrained – crisply free.
And of course, the same applies no matter which two dimension are consider the constrainers, which third dimension the resulting degree of freedom. All three are working together to exclude all other dimensionality and yet are also helping to create each other as what we recognise to be a spatial dimension – a place of free straight-line inertial motion.
There are some obvious unanswered questions here. How do we deal with the accelerations and decelerations of masses travelling within a straight-line? Why does that seem to be also a cost on the system, and how does that cost get measured if it is invisible to the other dimensions? Perhaps more importantly, what justifies all this talk of dimensions measuring each others existence, or having the urge to constrain dimensionality to some crisp minimum?
However, putting such concerns aside for the moment, the fact that continued motion in a straight line doesn’t need causing allowed Newton to make a great simplification in any model of physical reality. The old organicist physics of Aristotle had claimed that every motion required a constant cause. Effort could never let up. But Newton’s definition of inertia allowed the modeller to ignore the wanderings of masses between events like a collision. Unless acted upon by some other object or force, we can be sure that a mass will roll along at a steady speed in a straight line. So we don’t have to watch it every step of the way. All we need is a single measurement of its velocity – a reading of its speed and direction at some discrete instant. We can then calculate its future trajectory all the way up to its next interaction.
Newton's second law dealt with the causes of accelerations or changes in motion. The actual law states that for a given body, an acceleration is proportional to the force being applied and takes place in the direction of that force.
Again there is a deceptive simplicity in what was being claimed about Reality. Before Newton, a force was just a vague sort of idea to describe a pressure or tendency. Now it was being singled out as a crisply developed causal component – an actual thing in itself. Furthermore, forces were tied to the same straight-line geometry as masses. By definition, a push came straight in from one side and a mass got thrust in the precise opposite direction.
And even a complex combinations of pushes and pulls were reduced to a single force vector under Newton’s second law. Say there were two of us shoving a third person. The resulting force would be seen to act in a straight-line from some point roughly between us – exactly where depending on how hard we each happened to push. Even with a hundred of us involved, there would still be only a single resulting force vector according to Newton.
So his second law allowed the complexity of most real situations to be averaged away. All that was required was to measure an observed effect – how the motion of a body was changed – and a single discrete cause could be imputed. Many different balances of activity might have been the real cause, but for the sake of modelling, just one little arrow representing a certain push from a certain angle could stand for them all.
By splitting off the notion of force, the second law made for a more abstract notion of matter as well. It became the located resistance to match the located push. The second law became defined as the mathematical equation – F = ma. The force acting in some event is the amount needed to accelerate a mass in a certain direction. Or the formula could be switched around to m = a/F. The mass present at an event was betrayed by how much force had to be spent in producing an acceleration.
The directly measurable part of all this was the acceleration – the observer’s impression that something had deviated from its constant straight-line motion. Newton’s second law then dichotomised this impression into the asymmetric notions of force and mass! To one side went the idea of a localised resistance – something which “owned” a certain amount of inertia. To the other was the global context that had done the pushing. And just as any amount of pushes and shoves got reduced to a single force vector, so any amount of spread-about material got reduced to a single mass point. The force was modelled as pushing a mass in a straight line through its centre, its single point of balance.
The messy details of what a mass might be – a vast ragged cloud of gas, a mouldy marshmallow, a dense ball of lead – did not matter so far as the model was concerned. Under the second law, all such particular facts were washed away and matter represented by the resistance that would be shown by an idealised point at a single spatial location.
So we are beginning to appreciate the trick worked by Newton – how he excluded the organic to produce the mechanical. The first law defined matter as having inertial motion. Then the second law used inertial motion to separate every observed acceleration into its crisp mass and its crisp force. The yin of all the mute resistance was placed inside a point, the yang of all the causal drive was located just outside the point as a vector.
And of course the force vector was itself a result of dichotomising the globalness of space to create a foreground figure, the discrete shove, clearly visible against the empty backdrop that was all the space said not to have done any shoving. They certainly don’t call Newton’s approach reductionism for nothing!
And so we come to his third law of motion which states that
action there is an equal and opposite reaction. Every push creates a
push! If I shove you with force x, then you will shove me with force x
right back. And naturally these paired forces are tied to the geometry
of straight lines, being in precisely opposite directions.
The idea that a force always conjures up an opposing force is a little surprising. But the reality of the law quickly becomes apparent in weightless and friction free environments. Push someone on an ice rink and you would both glide away with equal momentum. It would not matter who put out the hand. Or when two balls strike on the baize of a billiards table, both will be equally deflected in opposite directions along a straight-line drawn through the point of impact.
Newton's law of action and reaction becomes less mysterious once you realise that it is a book-keeping exercise to correct for the fact that the Newtonian approach breaks the world down into a tale of one-way chains of cause and effect. A force - by definition - is an action in a single direction. Yet as we keep saying, Reality is actually woven of interactions. So causality must always be mutual in some way. The supposed doer and done-to need to have the properties that allow them to engage - to create an event, a strand of history - in the first place.
According to the third law, if a person pushes a door shut, the door is said to push just as hard against the person’s hand. A diagram would show two equal force vectors springing to life through the line of contact.
However what is really occurring is an interaction between two complex contexts. There is the door with all its material properties such as a certain structural rigidity, a relative lightness, and a low-friction hinge. Then there is the person with also a certain structural rigidity, a greater mass, and the ability to employ the frictional resistance of feet braced against the even greater bulk of the Earth. And so any interaction between hand and door will strike an emergent balance. In this case, the door will be seen to move a lot, a person and the earth very little.
Newton’s approach said this general impression could be reduced to a model in which the motion of the door betrays the presence of a discretely applied force. And then quickly to balance the books before more awkward questions are asked, the door also is said to have pushed back with an identical force.
The correctness of this becomes plainer if we think about it relativistically. Imagine watching the same door and person floating in deep space, far from any contextual landmarks to determine who moved, who stood still. All we could really say about this situation was that a hand and a door were observed to come together at an angle and then move apart in opposite straight-lines. Either or both sides might have been doing the shoving.
For all we know, the hand might have been outstretched when it got thwacked by a passing bit of space debris. The only visible fact is that the hand and door grew apart in distance. Each suffered an acceleration – and now instead of reading the story in terms of an asymmetric dichotomy between a force on one side, a mass on the other, we are seeing it as a simple symmetry of two mirror-image force vectors. Newton’s concept of mass tied it to located points. And once we become unsure about which side of an interaction counts as the located one, we have to allow each side to experience matching nudges.
gravity as action at a distance
Newton’s laws of motion led naturally to the
gravity. His three universal laws seemed to account for all possible
motions of bodies in space. Interactions broke down neatly into masses
and forces, an internal resistance to change and an external pressure
to change. For every observed effect, his mechanics allowed for the
dichotomous construction of the causal ingredients.
However the principle of inertia was a weightless description of Reality. It was a world in which gravity and friction had been discounted. Now they had to be reintroduced into the equations as themselves discrete forces. Friction seemed an easy one – it was just collisions with intervening masses. Any moving object would lose some of its oomph as it caught against other materials, imparting small forces randomly in all directions and so shedding speed as wasteful heat. But gravity was more difficult to place. Where friction seemed a highly local force, gravity must be something much more general.
The Austrian astronomer, Johannes Kepler, had already found that the planets followed elliptical orbits rather than simple circles. Not only this, but they also slowed down at the furthest reaches of their orbits, then speeded up as they swept close to the sun again. This was strange behaviour for those who felt that what heavenly bodies ought to move with stately perfection.
However Kepler realised that the yo-yoing of speed and distance meant that the planets were always carving out the same area of space in a given unit of time. There was an elastic balancing around an equilibrium point as if the planets were caught in the constant pull of a force like, perhaps, the recently discovered attraction of magnetism.
Revealing that Aristotelian organicism still had its grip on Renaissance thought, Kepler suggested that this gravitational force must be imparted by an aether-like material – the vis motrix – which was exuded by the spinning sun and then swept the planets along in its currents. Even an ardent mechanist like Descartes agreed that there could be no actual pushes and pulls without some physical medium actually in contact with the planets. He imagined it to be an atomistic sea of tiny particles – the matière subtile – that jostled the planets along. It took Newton's ruthless way with nature to cut away the intellectually unnecessary and simply model gravity as an immaterial force.
The story about an apple falling on Newton's head is probably another myth. But it was his crucial insight to see that gravity might be considered as a universal property of matter and so therefore a dropping apple would be pulling on the earth as much as the earth was pulling on the apple.
Again magnetism helped as it was already known to be a property of both small lumps of metal and the whole of the earth (as a turning compass needle showed). But Newton's principle of action and reaction - which as we have just seen, cleverly captures the organic mutuality of any physical interaction - said that any pushing or pulling must work two ways. So an apple had to accelerate the earth with a force to match the force being exerted on itself.
The second bit of the puzzle was to see that gravity was directly proportional to mass - to make the mathematical statement that multiplying the masses involved would multiply the force they experience by the same amount.
The final step was then to realise that - again like a magnet - the pull of gravity would dilute as it reached across space. If a mass was imagined to radiate a constant amount of force into the void, it would spread outwards from a point like a swelling sphere. So the force would thin as a square of the distance travelled simply because it would be smeared across a greater spherical surface area.
Once armed with the idea that gravity was a universal property of mass, Newton could explain the elliptical orbit of the planets. They must be balanced at the distance from the sun where the forward momentum of their inertia exactly matched the downward pull of gravity.
Newton imagined firing a cannon ball horizontally from the top of a high mountain. Gravity would pull the ball to earth, but the faster the velocity of the ball, the further it would travel before gravity had its effect. Eventually, if there was no atmosphere to create friction, the ball would reach a velocity where its forward speed exactly compensated for its rate of fall. The cannon ball would find itself forever dropping in a circular path around the earth.
Newton then saw the reason why comets, moons and planets actually move in stretched-out ellipses was that it was exceptionally unlikely they would first enter the gravitational field of the sun at precisely the right speed and angle to fall into a circular orbit. It is more likely that they would carry slightly too much or too little speed, or be a few degrees out of line. However a mass would then either find itself bending towards the sun, and so being accelerated as it became more head-on, or overshooting, and thus being decelerated as the sun began to drag from behind.
The result would be the yo-yoing of an elliptical orbit where during one phase, distance would be increasing but the speed of escape would be slowing, and on the other phase the speed would be increasing as the distance closed and gravity strengthened, but that extra momentum would eventually carry the planet safely back to the other side of its orbit.
In this way, like stars being compacted by their gravity then blown back out by the resulting heat of fusion, the solar system would be self-regulating. There would be no need for a hand of God to place heavenly objects in their perfect orbits. Within quite a wide range of masses, angles and speeds, the sun would be able to snare various lumps of debris into permanent and predictable trajectories.
the triumph of mechanics
Newton is hailed as history’s greatest scientist
the bold way he reduced the modelling of Reality to its bare
essentials. And his secret was to embrace the unreal even where it gave
For the organicist, the world is born out a dichotomous process of separation. It tends towards its asymmetric limits, yet also remains essentially unbroken. So it’s boundary states are unreal places in the sense they mark the point where the possible finally becomes the impossible. Boundaries can be approached infinitely closely yet never actually reached.
But the mechanical approach, as Newton finally made clear, is to accept the basic truth of dichotomies, then treat them as a crisp dualism. Instead of atom~void, it becomes atom/void. A triadic system in which there is a developing middle as well as two bounding limits becomes a simpler dyad of either/or. And then too often there follows the urge for a further reduction to a monad where one pole of Reality is taken as the more fundamental.
The Greek atomists had been the first with a clearly mechanical explanation of the world – one that took the crisp, isolate, existence of the materials for granted and so all development and change became a matter of bottom-up construction, a chain of cause and effect. However they fell into the trap of monism by arguing that all was either substance or non-substance, either the being of atoms or the non-being of the void. This was too simplistic as it reduced Reality to the thin symmetry of a presence and its absence.
What gives the symmetry-breaking of a dichotomy its explanatory power is the way the opposing poles become asymmetric in their character. They arise from a common ground yet end up becoming as unlike each other as possible. So Reality ends up with two very different aspects to its being.
The atomists certainly had this kind of asymmetry in the back of their minds when they came to talk about the void. As an infinite empty space to complement the extreme locatedness of atoms, the void’s not-being was actually the global to the atom’s local, the continuous to the atom’s discrete, the static to the atom’s change. But the atomists wanted to see substance as the only fundamental in their system and so they rejected any role for the obvious counterpart of form. The atoms constructed blindly and the void was not taken to have any particular formative properties.
As a picture of mechanical causality, atomism was suggestive. It certainly got the essentials of the causal process. Where organicism talks about a holistic, self-constraining, process of separating out, atomism was based on the idea of isolate sequences of cause and effect. But atomism lacked the rigorous framework to contain this causal mechanism.
Newton supplied it. Consider again the way he broke the Universe down to masses and forces existing in the void of space and time, but now governed by a set of universal laws. Starting with our confused impressions of the world, Newton identified accelerations as the real change. Motion in a straight-line was now stasis – that which needed no causal explanation as nothing was really happening. Then to account for accelerations, Newton dichotomised them into the discrete components of a force and a mass. A mover and a moved, a resistor and the overcomer of that resistance.
Mass and force were made atomistic substances in that they were modelled as crisply located, crisply existent. As later recognised by the conservation laws of physics, nothing gets destroyed during the mechanistic interactions of masses, just redistributed in space and time. The Universe is a closed system in which the fundamental materials only need creating the once.
Newton paved the way for yet other later insights. His crisp separation of mass from force led quickly to the idea of energy – a more clearly substance-based view of a force. And energy eventually became reunited with mass when Einstein saw they were two faces of the same coin – a return to the unbroken dichotomy of the organicist!
Newton was also responsible for that other essential dichotomy of physics – the separation of Reality into particles and fields. His three laws of motions talked about discrete force vectors acting on point-like inertial masses. In his mind, he actually had the picture of two masses like a pair of smooth round billiard balls physically colliding. The direct “particle on particle” contact could be seen, which removed a lot of tricky causal questions about the origins of the force and how it got communicated.
But Newton’s universal law of gravitation was quite different as it introduced the troubling concept of action at a distance. The accelerations due to the force of gravity were said to be communicated across empty space. Two masses could attract each other no matter how far apart they stood. The only thing that changed with distance was the strength of the pull being experienced by two locations.
Most of Newton’s contemporaries saw this as a step too far, and even Newton himself went back and forth on the subject, at times speculating that perhaps some Aristotelian-like aether might be drawing masses closer together. But in the end, physics decided the void had to remain empty and so forces like gravity, and later electromagnetism, became modelled as immaterial fields. The discretely located became the globally spread out once more.
And then later still there was the crowning irony in this organic reunification of the dichotomised. With Einstein demonstrating the essential equivalence of mass and energy, particles and fields became complementary concepts as well. A mass particle could be spread out as an immaterial field, an energy field could be reduced to the material exchange of particles.
In physics, even the simple is never simple. What gets broken must one day be put back together. But Newton was at least systematic and willing to stomach unreal notions like action at distance if the sums seemed to work out right. This intellectual rigour meant that where the atomists had dismissed the idea of a higher realm of form to organise their substances, Newton was not so shy. His own substances of mass and force quantified how much of certain kinds of stuff were to be found located at certain places. And then what guaranteed their behaviour were his universal laws – mathematical equations that like Plato’s forms were held to be timeless, eternal, unchanging, and outside the world of substance they controlled.
If you asked how a planet would actually know when to speed up to stay in an elliptical trajectory around the sun, or how a door could know to push back with equal force against a hand, then Newton’s answer was that it was the all-seeing eye of his laws that kept the realm of substance on track.
To take the laws of nature as things in themselves is of course unreal. For the organicist, they are just some kind of emergent boundary, an upper limit, on existence. Or as we might argue, they are in fact best considered as the Universe’s memory of what it should be – so indeed a kind of self-knowledge.
But for the sake of efficient modelling, Newton was as happy with an unreal image of the Universe’s forms as of its substances. This enabled him to sweep away all the messy details from the middle ground of existence. To one side went all that was the discrete, the located, the substantial. To the other went the continuous, the global, the lawful.
So with Newton the void became properly empty. Its continuity and dimensionality were made the responsibility of the universal laws. It was they who specified that masses and forces acted in straight-lines, who modelled the essential properties of space such as the dilution of forces with distance or the communication of gravitational effects without an intervening medium. Any of the causal features that seemed to go with being a big empty space, such as being permissive of the free play of substances, became wrapped up as impersonal forms that stood outside the Universe to which they gave order.
Newton trained the Western mind to see Reality a certain way. The mechanical view of causality is that it is a construction from crisp parts according to strict laws. A system starts with all its causes specified and the effects follow with matching inevitability. There is no room for creativity, no need for cohesive meaning. The story is closed in that the end is fixed from the moment it begins. In every way, a messy middle – a tale about vagueness – is excluded.
The mechanical view of course has its paradoxes. Mind becomes dualistically separated from matter. The strangely particular arrangement of particles and dimensions that forms our Universe has to be treated as a wildly unlikely accident – any impressions of purposefulness being just a sad anthropomorphic illusion. And the mechanical view created the problem of how a something could come from a nothing. Why anything when a continued nothingness would have been so much damn simpler?