Motion Transfer in Bodies

We impulsively think of motion in Body 1 as the cause of motion in Body 2.

When we consider these objects with utmost attention, we find only that:

• Body 1 approaches Body 2, and
• The motion of Body 2 comes from Body 1, but without any sensible interval.

It is in vain to rack ourselves thinking about this.

We can go no further in considering this particular example.

If anyone leaves this example and defines cause as something that produces another cause, then he would say nothing.

For what does he mean by ‘produce’?

Can he define it, that will not be the same with that of causation?

If he cannot, then he runs in a circle.

He gives a synonymous term instead of a definition.

Contiguity and temporal succession are not the basis of the idea of causation.

Causation needs a necessary, consequential connection.

The idea of consequential connection can be derived from impression.

When I view the known qualities of objects, I immediately discover that the relation of cause and effect does not depend on them.

I can find only their relations of contiguity and succession.

I have already regarded them as imperfect and unsatisfactory.

Does this mean that I have an idea which is not preceded by any similar impression?

This would be too strong a proof of levity and inconstancy, since the contrary principle has already been established.

Why must everything have a cause?

Why should such causes have such effects?

What is the nature of:

• that inference we draw from the one to the other?
• our belief in that inference?

The ideas of cause and effect are derived from:

• the ‘impressions of reflection’, and
• the ‘impressions of sensation’.

For brevity, I mention only the impressions of sensation as the origin of these ideas.

Though everything that I say of the impressions of sensation also extend to the impressions of reflection.

Passions are connected with their objects and with one another, just as external bodies are connected.

The same relation of cause and effect, which belongs to one, must then be common to all of them.