Mechanism attributes to motion three fundamental properties:-

1. Motion is the principle of all material activity; it is to be held to account for the birth of all new phenomena that occur in the universe.
2. It has the aptitude of transforming itself into numerous modes, such as heat, magnetism, electricity, light and weight.
3. It passes unchanged from one body to another, in a word it is transmissible..

Before undertaking to examine these propositions., we should be sure that we have a clear notion of what "motion" (or movement) means.

Metaphysical Analysis of Local Motion.

Aristotle suggested; "Movement is the actuality of a being which is formally potential" i.e. is capapble of having some further reality.

Movement is an actualization, a determination which it is necessary to distinguish from the simple power to act or to receive perfection in being.

A stone when lying still is susceptible of movement, but it is not yet in movement.

Movement begins when that susceptibility, or potentiality begins to be actualized.

It is therefore the actuality of a being still potential to possess further reality, to be something else.

Yet this actuality which gives bodies a new position and constitutes all the mobile reality of movement cannot be anything terminated or complete in all respects.

If you consider the stone which you have thrown into space, at the precise moment when it receives its new place, you can say that it has been moved, but it is no longer in movement. If then you wish to conceive it in the state of movement, you must consider it as on its way towards a new position, which is no longer its starting point nor yet its final resting place.

In other words, although determined by a new position, the moving object would appear in movement only on the condition of its being in proximate passive potentiality with regard to further actualization.

The actuality constitutive of movement is thus seen to a be an incomplete reality bearing a two-fold relation - on the one hand to a receiving or moveable subject which it determines by placing in a new position in space, and on the other to an ulterior perfection or a new position which the moving body continuously receives.
 
 

FIRST PRINCIPLE OF MECHANISM; Local movement is a force and a cause capable of producing a mechanical effect.

Criticism

According to the definition given above, movement comprises three elements indissolubly united.

1. First there is a movable thing in passive potentiality
2. An actuality or determination which realises the passive potentiality of the subject by giving it a new location.
3. And the tendency of the subject to receive hic et nunc other spatial determinations.

1. In virtue of its aptitude to pass from the state of rest to that of movement, the subject of movement manifestly cannot communicate anything or produce anything; it is capable only of receiving something under the influence of an external cause. Passivity, which excludes all dynamic power, is the essential characteristic of this first element which constitutes movement.
2. Whatever reality exists in movement consists in the continuous determination by which the body is fixed at each moment in different positions in space. Now this actualization has only this one effect, of giving to the body which receives it positions so fleeting that one disappears as another becomes real.
3. The tendency possessed by the moving body constantly to receive further actualizations is clearly a passive tendency and accordingly one incapable of producing an effect of any kind.

First objection

Is not every body in movement endowed with a dynamic power proportionate to the intensity of the movement by which it is animated?

Must we not then conclude that movement is the source of this energy?

A body in movement can certainly produce mechanical effects. Yet, the real cause of these effects is not the local motion, but a force properly so called, a motor-quality inherent in the mover.

In the first place, the study of movement proves that this accident is incapable of exercising efficient causality.

Secondly, experience confirms this deduction. A billiard ball which is at rest on the table may be put into motion by a sharp stroke of the cue. As long as the cue is in contact with the ball you can attribute the movement to the exercise of a force that is within the man who pushed the cue.

But once the contact has ceased and the player's action has ended, the cause of the movement which continues (and indeed would never cease but for exterior resistances) must lie elsewhere.

In fact, either the new positions of the ball are not real, and in this case it is foolish to attribute a dynamic power to this movement; or these new positions are real, and thus demand a permanent stable cause which is present during its effects and consequently resides in the moving subject itself.

For its is no longer the player who is producing the fleeting and constantly renewed series of the movement, for he has ceased altogether to influence the ball.

Whence comes this energy? It was communicated to the ball at the moment of shock; it is the immediate effect of the player's action, and the movement is only the result and partial measure of it.

Like all other qualities, this force is by its nature stable and permanent, and cannot be destroyed except by a contrary force.
 
 

Second Objection

Does not movement, when it has once been started, carry along in itself the principle of its continuity,, in the sense that every spatial position is itself the cause of the position which immediately follows it?

This hypothesis is overthrown by the Mechanists themselves. For to say that each position occupied by a body gives it the power of procuring the next is to affirm that matter at rest can by its own initiative communicate movement to itself, and thus defy the law of inertia.

The successive positions through which the body in motion passes in its action are not of a different nature from the last position where it comes to rest.

There is no real difference between them

If the first ones form part of the movement, it is solely because each supplies a stage in the process.
 
 
 
 

SECOND PRINCIPLE OF MECHANISM;

Movement is transmissible from one body to another
 
 

Criticism;

Like all other accidental realities, movement is made concrete and individual by the subject in which it inheres; it is dependent on it intrinsically and must remain attached to it, otherwise it would disappear from the world of reality.

The hypothesis that movement is transmissible is moreover condemned by experience. If two bodies meet, the one being in a state of motion, the other at rest, the result is that the moving body comes to rest and the stationary one is set in motion.

Now where does this new motion come from? Has it been transmitted from the body in the motion? Evidently not.

At the moment of contact, the moving body could not transmit the positions through which it had passed, since they no longer existed; nor again its present position, or else it would no longer have a place in space; nor again the future positions it could have received, since they still exist only in the domain of pure possibilities.

No particle of the movement of the moving body has then been transmitted to the body put in motion.

And as the new movement demands a cause, recourse must be had to the motor forces brought into play by the contact.
 
 
 
 

THIRD PRINCIPLE OF MECHANISM

Local Movement transforms itself into Heat, Electricity, Light, Magnetism etc.
 
 

All the forces of nature are said to be modes of movement that are capable of being transformed into one another.
 
 

Criticism

For one thing to be transformed into another, it is necessary

1. That it be deprived of some modes of being that characterize its present state, and
2. That part of the original thing remain in the final stage of the transformation.

Now in any case a new movement does not contain a part of the movement which preceded it.

For, the transitory actualizations which constitute the whole reality of movement are susceptible of two changes - changes of velocity and changes of direction.

Let us consider each of these:-

Change of velocity.

1. On receiving an impulse, a body already moving with a velocity of two metres a second acquires a speed twice as great. Now the only connexion there is between these two movements is that one succeeds the other.

To the series of positions occupied by the body in motion and now no more, at the moment of impulsion there succeeds a new series of transitory localizations.

It is impossible to see in this second phase of the phenomenon the least trace of the former phase.
 
 

Change of direction:

2. If a body in motion receives a lateral shock, it changes direction. Now in this new direction, be the motion rotary, vibratory or undulatory, one cannot discover any trace of the movement which preceded it, since at the moment of shock all the previous spatial determinations had completely disappeared one after the other

Hence movement is never the subject of any transformation.

It is true that the succession of the phenomena which we have just analysed awakens the idea of change, or rather of a certain transformation. But where mechanism errs is to place it in movement rather than in its real cause.

In the cases cited the motor force of the bodies, and that alone, has undergone the modifications or alterations which have produced the changes of velocity and of direction.
 
 

CONCLUSION

General reasons for the repudiation of Mechanism

First:

Mechanism has exaggerated the part played by movement and has falsified the notion by making it the Principle of all the changes that take place in the universe.

Hence arise contradictions when it is considered metaphysically, as well as its incapability to account for that vast array of facts where it is evident movement cannot take its origin from movement.
 
 

Secondly:

The second cause is its rejection of the teleological point of view in the explanation of scientific facts. The invariable recurrence of the same chemical and physical phenomena, the indissoluble union of fixed properties with fixed substances, in a word the cosmic order, demand a permanent and stable cause, an immanent directive power or principle of finality proper to each body and really specific.

But such a principle Mechanism rejects by substituting for it its dogma of the homogeneity of matter.
 
 

Thirdly:

A third cause is its reduction of all the forces of nature to different modes of local movement. Although all corporeal activities are accompanied by movement and on this account make the formation of mathematical physics possible, it is undeniable that they also present a qualitative and differential aspect which cannot be discovered in the modes of local movement, and this aspect mechanism fails to consider, thereby dooming itself to give but an incomplete explanation of the physical properties of matter.*

Furthermore the doctrine of the transmissibility and the convertibility of movement into light, heat, electricity and magnetism is the necessary consequence of the theory which reduces all to motion.

*DUHEM, Sur quelques extensions récentes de la statique et de la dynamique (in Revue des Questions scientifiques, Vol 1 April 1901)

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