| 17744 | De Morgan started the study of relations and their properties [De Morgan, by Walicki] |
| 13501 | De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [De Morgan, by Hart,WD] |
| 19238 | The logic of relatives relies on objects built of any relations (rather than on classes) [Peirce] |
| 8492 | Relations are functions with two arguments [Frege] |
| 10036 | In 'Principia' a new abstract theory of relations appeared, and was applied [Russell/Whitehead, by Gödel] |
| 21698 | All relations, apart from ancestrals, can be reduced to simpler logic [Quine] |
| 10816 | We can use mereology to simulate quantification over relations [Lewis] |
| 8525 | Relations need terms, so they must be second-order entities based on first-order tropes [Campbell,K] |
| 9926 | A relation is either a set of sets of sets, or a set of sets [Burgess/Rosen] |
| 9561 | The mathematics of relations is entirely covered by ordered pairs [Chihara] |
| 23627 | 'Before' and 'after' are not two relations, but one relation with two orders [Hossack] |