Secondness is one of the three universal categories of Charles S. Peirce. Through secondness, he focuses attention on the opposite of reaction, on the brutal fact of one thing as opposed to another.
The best example of pure secondness would be the unexpected collision of two things, the blow to the back of the head, or the pressure on something that does not lend itself to our attempts.
Accepting secondness as a universal category, Peirce argues that it is ubiquitous, wherever we go, we find resistance or resistance, although in most cases it is soft, sometimes completely negligible.
Secondness is close to what is now called another or otherness.
Related:
