Can our senses deceive us?

Can our senses deceive us? Where does the error of the senses come from?

We answer the question on external existence, by setting aside the metaphysical question of the identity of a thinking substance.

Our own body belongs to us.

Several impressions appear exterior to the body.

• These are also exterior to ourselves.

The paper I write on is beyond my hand.

The table is beyond the paper.

The walls of the room are beyond the table.

When I look out the window, I perceive a great fields and buildings beyond my room.

We might think that only the senses are needed to prove the external existence of body.

But this is wrong, as proven by 3 considerations:

Consideration 1: We do not perceive our body when we regard our arms and legs.

We perceive certain impressions which enter through our senses.

The ascribing of a real and corporeal existence to these impressions or to their objects, is an act of the mind that is difficult to explain.

Consideration 2: The mind commonly regards sounds, tastes, and smells as continued independent qualities.

They do not exist in space.

Consequently, they cannot appear to the senses as placed externally from the body.

Consideration 3: Even our sight does not tell us the distance immediately and without a certain reasoning and experience.

This is acknowledged by the most rational philosophers.

Any opinion that we create on the independence of our perceptions must be derived from experience and observation.

Our senses can never give us an idea of this independence.

Our conclusions from experience are not favourable to the doctrine of the independence of our perceptions.

When talk of real distinct existences of anything:

• we commonly mean their independent existence more than their external location, and
• we think that it has a sufficient reality if its being is continuous and independent of the changes in ourselves.

The senses cannot give us any notion of an object’s continued existence because they cannot sense the object continuously.

They cannot give us a notion of an object’s distinct existence, because the senses cannot offer the object to the mind:

• as represented, and
  • To offer it as represented, the senses must present both an object and an image.
• as original.
  • To make it appear as original, the senses must convey a falsehood.

This falsehood is in the relations and situation for the senses to compare the object with ourselves.

Our senses cannot do this and so our senses cannot deceive us.

Therefore, the notion of a continued and of a distinct existence never arises from the senses.

Three Kinds of Sensory Impressions

There are three types of impressions conveyed by the senses.

Type 1: Those of the shape, volume, motion and solidity of bodies.

Both philosophers and ordinary people think that these impressions have a continued existence distinct from each other.

Type 2: Those of colours, tastes, smells, sounds, heat and cold.

Only ordinary people regard these under the same category.

Type 3: The pains and pleasures arising from the application of objects to our bodies, such as the cutting of our flesh with steel.

Both philosophers and ordinary people, again, think these impressions to be merely perceptions.

Consequently, they are interrupted by and are dependent on the senses.

The senses perceive the existence of colours, sounds, and temperature in the same way as they perceive motion and solidity.

The difference we make between them in this respect, does not arise from the mere perception.

The prejudice for the distinct continued existence of colours, sounds, and temperature is so strong.

When the contrary opinion is advanced by modern philosophers, people imagine that:

• they can almost refute it from their feeling and experience, and
• their very senses contradict this philosophy.

Colours, sounds, etc. are originally on the same category with:

• the pain that arises from a wound, and
• the pleasure that proceeds from the heat of a fire.

The difference between pain and pleasure is founded on imagination, not on perception nor reason.

Both of them are just perceptions arising from the body’s configurations and motions.

Thus, pain and pleasre are in the same category as colors, sounds, etc.

To the senses therefore, all sensory perceptions are the same in the way that they exist.

We can assign a distinct, continued existence to objects, that we hear and see the colours of, without ever:

• consulting reason, or
• weighing our opinions by any philosophical principles.