Section 5


by David Hume Icon

Complex Ideas are Connected by Seven Kinds of Philosophical Relations

The word ‘relation’ is commonly used in 2 different senses*:

  1. A quality which connects 2 ideas in the imagination

This is the common meaning of ‘relation’ – one idea naturally introduces the other idea.

  1. An arbitrary union of 2 ideas in the imagination, which we compare those ideas with

This is the philosophical meaning of ‘relation’.

We extend this to mean any subject of comparison, without a connecting principle.

  • Thus, philosophers classify distance as a true relation, because we acquire an idea of distance by comparing 2 objects.

*Superphysics note: The 2 meanings show the 2 domains of physical and metaphysical reality

But we commonly say the following, as if distance and relation were incompatible:

  • “X is most distant from Y”
  • “A is most unrelated to B”.

It is an endless task to enumerate all those qualities:

  • which allow a comparison of objects, and
  • which produces the ideas of philosophical relation.

But they may be put under 7 general headings, as the sources of all philosophical relation.

The 7 Philosophical Relations

1. Resemblance

This is a common relation.

Without it, no philosophical relation can exist, since only resembling objects allow comparison.

Resemblance is necessary for all philosophical relations.

But it does not follow that it always produces a connection of ideas.

When a quality becomes very general and common to many individuals, it does not lead the mind directly to any one of them.

By presenting too many choices at one time, the quality prevents the imagination from fixing on any single object.

2. Identity

This relation is applied to constant and unchangeable objects, without examining the nature of personal identity.

Personal identity shall be examined afterwards.

This is the most universal relation.

It is common to every being which has any lasting existence.

3. Space and Time

After identity, these are the most universal and comprehensive relations.

These are the sources of an infinite number of comparisons, such as distant, contiguous, above, below, before, after, etc.

4. Quantity and number

This is another very fertile source of relation.

5. Quality

When any 2 objects have the same common quality, their degrees form another kind of relation.

One heavy object may be heavier or lighter than the other object.

Two colours of the same kind may be of different shades.

These allow a comparison.

6. Contrariety

This may initially be regarded as an exception to the rule, that no relation of any kind can subsist without some degree of resemblance. But only the ideas of existence and non-existence are contrary in themselves.

Existence and non-existence plainly resemble each other. Both imply an idea of the object, even if non-existence excludes the object from all times and places.

All other objects, such as fire and water, heat and cold, are only found to be contrary from:

  • experience, and
  • the contrariety of their causes or effects

7. Cause and Effect

This is another philosophical and natural relation

The resemblance in this relation, shall be explained afterwards.

Difference might be another relation.

But I consider it as a negation of relation, than as anything real or positive.

There are 2 kinds of difference, as opposed to identity or resemblance:

  • a difference of number
  • a difference of kind