Simple Ideas and Impressions

Generally, simple ideas and impressions are exactly correspondent, as the complex are formed from them.

How do simple ideas and impressions exist?

Which of the impressions and ideas are causes and effects?

The full examination of this question is the subject of the present treatise.

We shall establish a general proposition, that in their first appearance, all our simple ideas are derived from simple impressions which are correspondent to those ideas, and which those ideas exactly represent.

To prove this, I seek phenomena that are obvious, numerous, and conclusive.

First, I clarify the general proposition so that:

• every simple impression is attended with a correspondent idea, and
• every simple idea is attended with a correspondent impression

From this constant conjunction of resembling perceptions, I immediately conclude that:

• there is a great connection between our correspondent impressions and ideas, and
• the existence of the one has a considerable influence on that of the other.

Such a constant conjunction, in such an infinite number of instances, can never arise from chance.

It clearly proves a dependence of:

• the impressions on the ideas, or
• the ideas on the impressions.

I then consider the sequence of their first appearance to know on which side this dependence lies.

By constant experience, I find that the simple impressions always precede their correspondent ideas, but never appear in the contrary order.

To give a child an idea of scarlet or orange, of sweet or bitter, I present the objects.

I convey to him these impressions.

But I do not absurdly try to make him produce a red object by making him think about the red colour.

Our ideas on a thing does not lead to that thing existing as an impression in reality.

We cannot perceive any colour or feel any sensation by merely thinking of them.

On the other hand, we find that any impression is constantly followed by an idea which resembles it.

It is only different in the degrees of force and liveliness.

The constant conjunction of our resembling perceptions is a convincing proof that the one are the causes of the other.

This priority of the impressions is an equal proof that our impressions are the causes of our ideas, not our ideas of our impressions.

Exception and Limitation of the General Maxim

If the senses are faulty, as when one is born blind or deaf, the impressions and their correspondent ideas are lost.

Their smallest traces never appear in the mind.

This is true where the senses are:

• entirely destroyed, and
• never used.

We cannot create an idea of a pineapple’s taste without tasting it.

However, one contradictory phenomenon proves that it is not absolutely impossible for ideas to go before their impressions.

The colours or sounds conveyed by the senses, are really different from each other even if they resemble. If this is true of different colours, then it must be also true of the different shades of the same colour.

Each of the shades produces a distinct idea independent of the rest. If this is denied, then it would be possible to for a colour at its lightest shade to be called the same thing as the same color in its darkest shade.

Suppose a person enjoyed his sight for 30 years.

• He has seen all colours, except one shade of blue which he has never seen.
• Place all the shades of blue before him descending from the deepest to the lightest, without that one.
• He will perceive a blank where that shade is missing.
• He will then find out that there is a greater distance in that place between the contiguous colours, than in any other.

From his own imagination, can he:

• supply this deficiency? or
• create the idea, by himself, of that shade that he has never seen?

I believe a few will think that he can.

This may serve as a proof that the simple ideas are not always derived from the correspondent impressions.

Though the instance is so particular and singular, it:

• is not worth observing, and
• does not merit changing our general maxim.

Other people might suggest an additional exception that our secondary ideas are images of our primary ideas, and so are not derived from impression.

However, this is not an exception because those primary ideas are simple ideas which are supposed to be derived from impressions.

Generally, There are No Innate A Priori Ideas

This is the first principle that I establish in the science of human nature.

This question on the sequence of our impressions or ideas is the same as the question whether:

• there are any innate ideas [ a priori ], or
• all ideas are derived from sensation and reflection. [ a posteriori ]

To prove that the ideas of space and colour are not innate, philosophers only show that ideas are conveyed by our senses.

To prove that the ideas of passion and desire are not innate, they say that we already have an experience of these emotions in ourselves.

These arguments only prove that ideas are preceded by other more lively perceptions:

• from which they are derived, and
• which they represent.