From Paul Phillips:
I see adjoint functors.
How often do you see them?
All the time. They’re everywhere. pic.twitter.com/6PkGJ9wP4A
— Paul Phillips (@contrarivariant) May 27, 2017
Mashup of Saunders Mac Lane’s quip “Adjoint functors arise everywhere” and Haley Joel Osment’s famous line from Sixth Sense.
Related: Applied category theory