Basically, reality and the world could be understood through the human intellect alone. Deism and utilitarianism are two philosophies that emerged from the Enlightenment, showing clearly the mindset of the age. Deists say that nature proves there is a God. He is, however, no longer involved in His creation. No longer is He needed.
Utilitarianism approaches moral problems by whether their effect on society is positive or negative.
Stealing is wrong only because it disturbs society. No longer is it a moral issue-it has become a social one. Deism and utilitarianism are only two examples of the intellectual mindset of the Enlightenment period, which lasted from 1789-1889. During the 20th century the movement peaked and became modernism. Modernism was essentially the Enlightenment with a slightly different twist.