Darwin’s Descent of Man was published in 1871 and is Darwin’s second book on his theory of evolution and natural selection. It follows his original work, published a decade earlier, called On the Origin of Species. The Descent of Man focused on applying the theory of evolution to the development of the human species.

Jeremy Bentham was a radical thinker on a number of levels, arguing that decisions should be made based on effecting the most good for the largest number of people. In education, Bentham was perhaps the most radical, but also the most influential. Bentham argued that the then contemporary practice of making education only available to Anglicans who could afford Oxford and Cambridge was wrong. Bentham's ideas were central to the founding of University College London in 1826, which sought to admit students based wholly on merit rather than religion and wealth.

Many of these writers were critical of Christianity in one form or another, but only Nietzsche famously suggested that religion was abhorrent and a distraction from the pursuit of individual truth or meaning. Nietzsche's emphasis on individual subjecthood directly contrasted religious notions of sacrifice, humility, and hubris. Nietzsche’s ideas were widely influential encouraging the growth of nihilism and existentialism and challenging religion's claim as the correct path to truth and meaning.

Throughout the Medieval period of European history, most scholarly pursuits, including writing, were almost exclusively the prerogative of monks and other clergymen. The vast majority of Europeans had neither the education nor the free time to undertake intellectual pursuits, and the noblemen and kings were often more interested in making war and enjoying life. This left the role of scholar occupied almost exclusively by members of the church. Their writing generally reflected their absolute faith in the divine and their belief that the earthly life was merely a preparation for the afterlife.

A famous quotation, usually attributed to Alexander Pope about the importance of the work of Isaac Newton, had direct bearing on this question: “Nature, and nature’s laws, lay bathed in night. God said ‘Let Newton be!' And all was light.” Isaac Newton’s most famous contribution to science was to prove that gravity was the primary driving force behind the movement of planets and of objects on Earth. His research proved that the universe could be explained independently of divine will, ushering in a new era of scientific inquiry and skepticism.

Like all great scientists, Isaac Newton’s work is simultaneously brilliantly original and deeply reliant on the tradition of scientific inquiry and discovery in which he was participating. When Newton developed his laws of motion and gravity, he was building, specifically, on the work of Galileo and Kepler (and to a lesser degree Copernicus) on the movement of planets and the Earth’s place in the universe.

Humanism emerged in the thirteenth, fourteenth, and fifteenth centuries in the Italian city-states. The emergence of Humanism coincides with the beginning of the Renaissance in Europe. Humanism was an artistic and intellectual movement, and also a literary movement; prominent examples of humanist literary writing include Erasmus and Petrarch. Humanist literary writing represented a shift in the focus of many writers and thinkers from the divine to the temporal, as in Petrarch's sonnets, which focus entirely on earthly love and unrequited desire.

David Hume was a Scottish philosopher in the eighteenth century. He is widely considered to be one of the most influential philosophers in British history and one of the pioneers of empiricism and skepticism in Britain. His most famous work A Treatise of Human Nature attempts to empirically examine the psychological basis of human behavior. Hume firmly believed that people could not have innate ideas, but could only have an understanding based on the things they had directly experienced.  

Francis Bacon was an English scientist who is often credited with coming up with what is now known as "the scientific method." Bacon believed that scientific inquiry was too often conducted with the incorrect spirit, or with the wrong intentions. He advocated for inductive reasoning that prioritized observation and the collection of data above the sporadic and unsupported development of theories based on tradition that had previously dominated scientific inquiry. The general principle of inductive reasoning is to build one's larger theories about phenomena on an accumulated base of smaller, quantifiable observations.

The primary emphasis of most writers of the Renaissance, particularly those who ascribed to humanism, was to consider and celebrate the human experience. Humanist writers celebrated the possibility of all people to better their world and focused much less on religious considerations then had their counterparts in the Medieval Era. This is not to say that Renaissance humanists were all atheists; many were deeply religious. They simply sought to turn their intellectual pursuits toward more open and nuanced treatments of human endeavor and experience.