Page "Definition" Paragraph 34

# Definitions should avoid circularity.

To define a horse as ' a member of the species equus would convey no information whatsoever.

For this reason, Locking adds that a definition of a term must not comprise of terms which are synonymous with it.

This would be a circular definition, a circulus in definiendo.

Note, however, that it is acceptable to define two relative terms in respect of each other.

Clearly, we cannot define ' antecedent ' without using the term ' consequent ', nor conversely.