Section 5

More Objections

by David Hume Icon

The Idea of Space is Just Made Up of Points

The second part of my system is that the idea of space is just the idea of visible or tangible points distributed in a certain order.

If this is true, it follows that we cannot form an idea of a vacuum or space where there is nothing visible or tangible.

This creates three objections which I shall examine together because the answer for one is related to the answers for the others.

  1. For many ages, men have disputed a vacuum and a plenum [ a space filled with matter], inconclusively.

Philosophers think themselves free to take part on either side. But the very dispute is decisive on the idea. It is impossible men could so long reason about a vacuum and refute or defend it, without knowing what they refuted or defended.

  1. The reality or possibility of the idea of a vacuum is proven by the following reasoning.

Every idea is possible. The world is currently a plenum. But we can easily conceive it to be deprived of motion. We can easily conceive an omnipotent diety destroying any part of matter while the other parts remain at rest since: every idea that is distinguishable is separable by the imagination, and every idea that is separable by the imagination can exist separately. The existence of one particle does not imply the existence of another particle. If the Deity Destroyed Matter, How Will the Universe React? So what happens when the ideas of rest and annihilation are combined?

What follows the annihilation of the air and subtle matter in the room, if the walls remained the same?

Some metaphysicians answer that since matter and space are the same, the annihilation of the contents of the room makes the walls of the room collapse into each other and touch each other. They would touch each other because there would be no distance between them. This answer is very common. But I defy these metaphysicians to: conceive the matter according to their hypothesis, or imagine the room’s floor, roof, and walls, to touch each other. If you change their position, then you suppose a motion. But as we stay strictly with annihilation and no motion, the result would be a vacuum and not a contact of parts. 3. The idea of a vacuum is real and possible, necessary and unavoidable.

This assertion is founded on the motion of bodies. This motion would be impossible and inconceivable without a vacuum, into which one body must move to make way for another. I shall not enlarge on this objection because it belongs to natural philosophy. To answer these objections, we must:

take the matter pretty deep, and consider the nature and origin of several ideas. Otherwise, we will dispute without understanding the issue. Darkness is Not the Same as Vacuum, Since a Vacuum is Absolute Nothingness The idea of darkness is not a positive idea.

It is merely the negation of light or coloured and visible objects. A man who enjoys his sight, receives no perception when entirely deprived of light just as a man born blind. A man born blind has no idea of light or darkness. The consequence of this is: that it is not from the mere removal of visible objects that we receive the impression of space without matter, and that the idea of utter darkness can never be the same with the idea of vacuum. Floating Man

Suppose a man were supported in the air and softly conveyed along by some invisible power.

He is sensible of nothing. He never receives the idea of space nor any idea from this invariable motion. Even if he moves his limbs, this cannot convey to him the idea of space. He feels successive sensations which may give him the idea of time. But his sensations are not disposed in a way to convey the idea of space. Therefore, darkness and motion, with the removal of everything visible and tangible, can never give us the idea of a vacuum.

All bodies seen by the eye, appear as if they were painted on a plain surface. This makes their distance to us appear uniform. This distance is discovered more by reason than by our senses. When I hold up an object to the sky, it is surrounded by the blue sky just as well as it could be surrounded by other visible objects.


Can sight convey the impression and the idea of a vacuum? For this, we must suppose that there are luminous bodies presented to us amidst darkness. Their light discovers only these bodies themselves, without giving us any impression of the surrounding objects. We then create a parallel supposition on physical tactile objects.

We cannot suppose a total removal of all tactile objects. We touch an object and then touch another and so on. Do these intervals afford us the idea of space without body? Lights

When only two luminous bodies appear to the eye, we can perceive whether they are:

conjoined or separate, and separated by a great or small distance. If this distance varies, we can perceive its increase or decrease with the motion of the bodies. But as the distance in this case is not anything coloured or visible, it may be thought that here is a vacuum or pure space intelligible to the mind and obvious to the very senses. This is our natural and most familiar way of thinking.

We shall learn to correct this by a little reflection. When two bodies present themselves, where there was formerly an entire darkness, the only discoverable change is in the appearance of these two objects. All the rest continues to be as before, a perfect negation of light and every visible object. This is true of what are remote from these bodies and the very distance between them. This distance is nothing but darkness or the negation of light. It has no parts nor composition. It is invariable and indivisible. Since this distance causes no perception different from what a blind man sees or what we see in darkness, it must share the same properties. Blindness and darkness afford us no ideas of space. It is impossible that the dark and undistinguishable distance between two bodies can ever produce that idea. The sole difference between an absolute darkness and the appearance of two or more visible luminous objects is in the:

objects themselves, and the way they affect our senses. Sight and Touch Alone Cannot Convey the Idea of a Vacuum The following produce the only perceptions which we can judge of the distance:

the angles of the rays of light flowing from them, forming with each other, the motion required in the eye, in its passage from one to the other, and the different parts of the organs affected by them. Each of these perceptions are simple and indivisible.

They can never give us the idea of space. We may illustrate this by considering:

the sense of feeling, and the imaginary distance or interval between tangible or solid objects. Two men are suspended in the air.

One man moves his arm around without hitting anything tangible. Another man moves his arm around and hits an object. His arm leaves it, moves again, and hits another object. What is the difference between these two cases?

The difference is merely in the perception of those objects. The sensation arising from the motion is the same in both cases. That sensation cannot: convey to us an idea of space when there is no other perception, nor give us more of that idea of space when mixed with the touch of tangible objects, since that mixture does not change the space. Motion and darkness, either alone or lacking any tangible and visible objects, convey no idea of a vacuum.

But darkness and unhindered motion are why we falsely imagine that we can create the idea of a vacuum, because there is: a close relation between that motion and darkness, and a real space between visible and tangible objects.

  1. Two visible objects in utter darkness makes us see a gap between them, which our minds can fill with objects that can give us a true idea of space.

The sensation of motion is likewise the same when there is nothing tangible between two bodies. 2. Two green balls have a gap between them filled with two more balls and are placed in the same way as two yellow balls.


Our senses will see that the two yellow balls can receive the same space without us touching them. Similarly, we can detect the space between those yellow balls when we run our hand between them and feel no objects other than those two. In other words, without changing the two yellow balls: our imagination can convert an invisible distance into a visible one, and our sense of motion can convert an intangible distance into a tangible one. 3. These two kinds of distance have nearly the same effects on every natural phenomenon.

All qualities, such as heat, cold, light, attraction, etc. reduce in proportion to the distance. There is little difference whether this distance is: marked by compounded and sensible objects, or known only by how the distant objects affect the senses. Here then are three relations between that distance which conveys the idea of a space and a vacuum.

The distant objects affect the senses in the same way, whether separated by space or a vacuum. The second species of distance is found can receive the first. A space and a vacuum both equally reduce the force of every quality. These relations between a space and a vacuum will afford us an easy reason why:

the one has so often been taken for the other we imagine we have an idea of space without the idea of any visible or tangible object. We may establish it as a general maxim in this science of human nature, that wherever there is a close relation between two ideas, the mind tends to mistake them and use the one for the other in all its reasonings.

This happens so often that I must examine its causes. But first, we must: distinguish exactly between the phenomenon itself and its causes, and not imagine that the phenomenon is from any uncertainty in the causes, that also uncertain. The phenomenon may be real, but my explanation might be chimerical. The falsehood of the one is no consequence of the falsehood of the other. I mentioned resemblance, contiguity, and causation, as principles of union among ideas, without examining their causes so that I could prosecute my first maxim.

We must be content with this maxim for the lack of something more plausible. It would be easier to dissect the brain and observe why the animal spirits run through all those relations when it thinks of any idea, and rouses up the other ideas related to it. The mind is endowed with a power of exciting any idea it pleases, whenever it dispatches the spirits into that region of the brain where the idea is placed.

These spirits always excite the idea when they: run precisely into the proper traces, and rummage that cell which belongs to the idea. Their motion: is seldom direct, and naturally turns a little to the one side or the other. This is why the animal spirits, falling into the contiguous traces, present other related ideas in lieu of that idea which the mind desired to survey at first.

We are not always sensible of this change. Continuing the same train of thought, we make use of the related idea, which is presented to us, and employ it in our reasoning, as if it were the same with what we demanded. This is the cause of many mistakes and sophisms in philosophy. Resemblance is the most fertile source of error of the three relations above-mentioned.

Resembling ideas are related together. The mind’s actions which we employ in considering them are so similar, that we are unable to distinguish them. We therefore take the one for the other. Causation and contiguity may also create mistakes.

This is seen in poets and orators. We use words for ideas. Words are so commonly closely connected, that the mind easily mistakes them. The idea of distance is not visible nor tangible.

This is why we substitute the idea of a distance with the idea of space. Causation and resemblance creates this mistake. This is because the mind converts the invisible and intangible distance into the visible and tangible distance, as space. In this respect, the invisible distance is a kind of cause, while the similarity of their way of affecting the senses, and reducing every quality, creates the resemblance. I can now answer all the objections from metaphysics or mechanics.

A vacuum is a space without matter. The frequent disputes about a vacuum do not prove the reality of the idea of a vacuum. Men most commonly deceive themselves in this, especially when there is another related idea presented which can become the cause of their mistake. We may almost make the same answer to the second objection, derived from the conjunction of the ideas of rest and annihilation. When everything is annihilated in the room and the walls stay immovable, the room must be conceived in the same way as at present. Presently, the air that fills it is not an object of the senses. This annihilation gives the eye that fictitious distance discovered by: the different parts of the organ that are affected. the degrees of light and shade the feeling from a motion in the hand. We should not search any farther. On whichever side we turn this subject, these are the only impressions that such an object can produce after the supposed annihilation. Impressions can only give rise to resembling ideas. Since a body interposed between two other bodies may be annihilated without producing any change on either hand of it, we can easily conceive how any change may be:

created anew yet produce as little alteration. The motion of a body has much the same effect as its creation.

The distant bodies are no more affected in the one case, than in the other. This satisfies the imagination. It proves there is no repugnance in such a motion. Afterwards, experience persuades us that: two bodies situated in the above manner, really have such a capacity of receiving body between them, and there is no obstacle to the conversion of the invisible and intangible distance into one that is visible and tangible. However natural that conversion may seem, we cannot be sure it is practical before experiencing it.

Thus, I have answered the three objections above-mentioned. Few will be satisfied with these answers. They will immediately propose new objections. They will probably say: that my reasoning makes nothing to the matter at hand, and that I explain only how objects affect the senses, without trying to account for their real nature and operations. There is nothing visible or tangible in between two bodies. Yet we find by experience, that the bodies may: be placed in the same way to the eye, and require the same motion of the hand in passing from one to the other, as if divided by something visible and tangible. This invisible and intangible distance is also found by experience to contain a capacity of: receiving body, or becoming visible and tangible. Here is the whole of my system. I have not tried to explain the cause which: separates bodies this way gives them a capacity of receiving others between them, without any impulse or penetration. I answer this objection by:

pleading guilty, and confessing that my intention never was to: penetrate into the nature of bodies, or explain the secret causes of their operations. This does not belong to my present purpose.

I am afraid that: such an enterprise is beyond the reach of human understanding, and we can never pretend to know body otherwise than by those external properties discovered through the senses. People might attempt anything further.

But I cannot approve of it until I see someone who has succeeded. Presently, I content myself with knowing perfectly: how objects affect my senses, and their connections with each other, as far as experience informs me of them. This is enought for the conduct of life. This is also enough for my philosophy, which only explains the nature and causes of our perceptions [Footnote 4]. Footnote 4

As long as we confine our speculations to the appearances of objects to our senses, without entering into a long essay about their real nature and operations, we: are safe from all difficulties, and can never be embarrassed by any question. Thus, if asked whether the invisible distance between two objects is something or nothing, it is easy to answer that it is something, namely a property of the objects which affect the senses If asked whether two objects with a distance between them touch or not, it may be answered that this depends on the definition of touch. Objects touch if they touch when there is nothing sensible between them. Objects do not touch, when: their images strike contiguous parts of the eye, and the hand feels both objects successively, without any interposed motion. The appearances of objects to our senses are all consistent. No difficulties can ever arise, but from the obscurity of the terms we use. If we carry our inquiry beyond the appearances of objects to the senses, most of our conclusions will be full of skepticism and uncertainty. There are no very decisive arguments on either side, if asked whether the invisible and intangible distance is always full of: body, or something that might become visible or tangible by an improvement of our organs. I am inclined to the contrary opinion as being more suitable to vulgar and popular notions. If the Newtonian philosophy is rightly understood, it will be found to mean no more. It asserts that a vacuum is where bodies are placed in such a way to receive bodies between them, without impulsion or penetration. The real nature of this position of bodies is unknown. We are only acquainted with its: effects on the senses, and power of receiving body. The following are most suitable to that philosophy: a modest skepticism, and a fair confession of ignorance in subjects that exceed all human capacity. The foregoing reasoning will explain a paradox: if ‘vacuum’ is the name of the invisible and intangible distance, then space and matter are the same.

Yet there is a vacuum. If you do not call the invisible and intangible distance as a ‘vacuum’, then motion is possible in a plenum without any impulse to infinity, without penetration and without returning in a circle. We must always confess that we have no idea of any real space without:

filling it with sensible objects, and conceiving its parts as visible or tangible. The doctrine, that time is nothing but how some real objects exist, is liable to the same objections as the similar doctrine on space.

If we have the idea of a vacuum because we reason on it, we must also have the idea of time without any changeable existence, since time is the most frequent and common subject of dispute. But we really have no such idea. Where should we derive time from? Does it arise from an impression of: sensation? or reflection? Point it out distinctly to us, that we may know its nature and qualities.

But if you cannot point it out, you are certainly mistaken when you imagine you have any such idea. It is impossible for an unchangeable object to give us an impression from which we get the idea of time.

But we can easily point out the successive appearances of such an unchanging object which then make us imagine that we have the idea of time. There is a continual succession of perceptions in our mind. The idea of time is forever present with us. If we think of an unchanging object now and then 5 seconds later, the object appears twice in our minds. This makes us impose the fictitious idea of time on that object in the same way as if the object had changed between those two appearances. The more appearances the unchanging object has in our minds, the more of the fictitious time we assign to it. These relations confound our ideas and make us imagine that we can create an idea of time without any change.


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