The first philosopher who approached the problem of reality from a "scientific" lens and also the first thinker who dabbled into the complex problematization of the end goal of life: happiness
JohnStuart Mill declared the Greatest Happiness Principle, that an action is right as far as it maximizes the attainment of happiness for the greatest number of people
Democritus and Liucippus led a school whose primary belief is that the world is made up of and is controlled by the tiny indivisible units in the world called atomos or seeds.