What are the reasons for the adjuction symbol $F\dashv G$ for a pair of functors $F:C\to D$ and $G:D\to C$? There is no explanation or motivation in the article of [Kan](https://www.ams.org/journals/tran/1958-087-02/S0002-9947-1958-0131451-0/S0002-9947-1958-0131451-0.pdf) where adjunctions are introduced.


The question was previously asked on [MathStackExchange](https://math.stackexchange.com/questions/4891701) without getting an answer.