From "The Yoneda Perspective", a 2017 essay by Tai-Danae Bradley, discussing the Yoneda Lemma of Category Theory:
... mathematical objects are completely determined by their relationships to other objects ...
... and:
... the properties of a mathematical object are more important than its definition ...
... and in the remarks on that essay, a comment by David Roberts:
| Q: "What is the Yoneda lemma? And if it's just a lemma then - my gosh - what's the theorem?" A: "All of them." |
(cf Tai-Danae Bradley's blog and her 2018 notes "What is Applied Category Theory?"...) - ^z - 2018-10-03