The purpose of philosophy is not to pursue knowledge for its own sake, but to bring about peace of mind and body.
Happiness is peace of mind and body.
The soul and the body are composed of indivisible small particles called atoms. The human body is composed of coarser atoms that tend to hold together. The human soul is composed of very fine and smooth atoms that are dispersed, if they are not held in by the body. Atoms are constantly moving through the universe forming compounds. They generally move in a straight line, but they sometimes swerve, bumping into other atoms, vibrating back and forth and forming compounds.