Humanity as a collective has always pursued a socially specific ideal mode of existence. Individually, humans form identity and purpose uniquely and according to distinct beliefs and values.
The pursuit of happiness has always been subjective. There will always exist those who believe that in serving their own intentions and desires they bring meaning to their life. Those who that claim that pleasure is the highest good, and live by the ethos that whatever causes pleasure is right. This is the aim of Hedonism.
Human behaviour, at its most fundamental level, has long been determined not by any arbitrary code of morality, but by the sensations of pain and pleasure, and the avoidance of one over the other.
"Nature has placed mankind under the governance of two sovereign masters, pain, and pleasure. It is for them alone to point out what we ought to do, as well as to determine what we shall do"
-Bentham
"We recognise pleasure as the first good innate in us, and from pleasure we begin every act of choice and avoidance, and to pleasure we return again, using the feeling as the standard by which we judge every good."
-Epicurus | 
