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5. Theory of Logic / E. Structures of Logic / 6. Relations in Logic

[role of terms which connect objects into relationships]

9 ideas
De Morgan started the study of relations and their properties [Walicki on De Morgan]
De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [Hart,WD on De Morgan]
The logic of relatives relies on objects built of any relations (rather than on classes) [Peirce]
Relations are functions with two arguments [Frege]
In 'Principia' a new abstract theory of relations appeared, and was applied [Gödel on Russell/Whitehead]
We can use mereology to simulate quantification over relations [Lewis]
Relations need terms, so they must be second-order entities based on first-order tropes [Campbell,K]
A relation is either a set of sets of sets, or a set of sets [Burgess/Rosen]
The mathematics of relations is entirely covered by ordered pairs [Chihara]