Bertrand Russell's 'The Conquest of Happiness' emphasizes that true happiness arises from the pursuit of pleasure, which he defines as overcoming obstacles that foster creativity. He argues that cooperation and association among individuals are crucial for achieving happiness, which cannot flourish in a competitive or disintegrating society like capitalism. Ultimately, Russell asserts that happiness is linked to a deep interest in the world and the essential condition of feeling loved, highlighting a unity between one's inner self and the external environment.