Even though the UNIX system introduces a number of innovative programs and techniques, no single program or idea makes it work well. Instead, what makes it effective is an approach to programming, a philosophy of using the computer. Although that philosophy cannot be written down in a single sentence, at its heart is the idea that: 

the power of a system comes more from the relationships among programs than from the programs themselves.

- Brian Kernighan, <UNIX Programming Environment>

philosophy