In his The Course of Positive Philosophy, Auguste Comte famously divided the history of societies up into three main periods. These periods are said to be characterized by their manners of explaining the causes of human experience. The first is the theological phase. In this stage, causes are explained primarily in terms of gods or a god. Then, in the "metaphysical" stage, abstract notions are used to explain the causes of things. Finally, in the "positive" stage, only "positive" (or posited) facts and scientific observations are the primary mode of explanation. Comte thought the final type of society was the highest and most developed. By doing so, he set up his own time's philosophical conception of knowledge as the pinnacle of human thought.

Immanuel Kant was the inheritor of the great pedagogical program of German scholasticism, drawing on a number of thinkers such as Wilhelm Gottfried Leibniz (especially through the works of Christian Wolff) and many, many others. At a certain point in his career, however, Kant came to the conviction that the excesses of these so-called "rationalistic" philosophers could not provide an adequate grounding for the sciences and for the moral life.

Therefore, Kant undertook a change of perspective that led to the publication of his three best known works: The Critique of Pure Reason, The Critique of Practical Reason, and The Critique of Judgment. These three texts sought to explain just what could be known within the bounds of finite human reason—thus providing a critical perspective regarding what he took to be the excesses and emptiness of the philosophy that he had taught for many years.

The notion of "Cartesian Dualism" is named after the thinker René Descartes(1596-1650)—a man who is often seen to be one of the fathers of modern philosophy. In his Discourse on Method and his Meditations on First Philosophy, Descartes makes a number of famous arguments. One of the most well known ideas is that the soul is completely distinct from the body. He concludes this from the idea that thought is clearly distinct from the notion of "body." The latter is really more of a geometrical "stuff" than anything else. He claims that even if we didn't have a body, we could still have self-consciousness.

His arguments are more complicated than this, of course, and they are open to many critiques. Be that as it may, one of the hallmarks of his philosophy is this kind of "dualism." In general a "dualism" occurs when we explain something through two different, unique principles that are not reducible to each other. Thus, for him, the human person is reduced to these two principles: soul and body. It's up to the philosopher to try to puzzle out how they are related.

In a way, all of these thinkers were influential, though in different ways. Francisco de Vitoria was a teacher in Spain whose work on natural rights is part of a broader discussion that would eventually filter through many Catholic and Protestant thinkers. These thinkers would become sources for the pivotally important Thomas Hobbes, whose best known political work is the Leviathan—a brutal but fully developed treatise on a quite domineering notion of the nation state. Likewise, Baron de Montesquieu was quite influential on many political thinkers during this period, as was Jean-Jacques Rousseau.

The most important thinker concerning the Declaration of Independence is John Locke. It is from Locke's thought that Thomas Jefferson derived his remarks regarding the rights to "life, liberty, and the pursuit of happiness." In Locke's political philosophy, he actually presents life, liberty, and property as the three fundamental rights of human persons. Locke's position was a kind of softening of the much harsher position of Hobbes, who stated that when we are not in society, we only have one fundamental right—self defense! Note, of course, that Jefferson changed "property" to "pursuit of happiness." This followed the recommendations of his fellow drafters, who hoped thereby to avoid issues that could have arisen because of a very problematic form of property in the colonies—slaves.

In his political philosophy, Jean-Jacques Rousseau discusses (among other things) the idea of the "general will" of the people. This idea can seem very horrifying—almost like a tyrannical will of the majority over the rest of the people. He means something much simpler than that. He is merely referring to the idea that in a given group of people, the people as a whole have a will that is aimed at certain common goals. Indeed, in some ways, Rousseau's thought in this regard is a kind of strange version of what some Aristotelians and Medieval Scholastics meant in their discussions of how the common good is willed by a political body. Of course, there are great differences in how they conceived of the common good and how Rousseau discussed the "general will." What remains, however, is the fact that Rousseau is, in fact, well known for using this notion in his political philosophy.

Epicureanism takes its name from Epicurus, the Greek philosopher from the third and fourth centuries BCE, who argued for "pleasure" as the goal for all human beings to reach transcendence. Epicurus did not strictly advocate seeking unadorned hedonism, but instead saw "pleasure" as best achieved through a moderate approach to life. Epicureanism was very popular in Classical Antiquity, but died out after the rise of Neo-Platonic and Christian thought in the third and fourth centuries CE.

In the Bible, the books of Exodus through Deuteronomy tell of the departure of the Hebrew people from Egypt. The classic moment in this sojourn is their time at Mount Sinai. This is where the so-called Ten Commandments were said to be presented by God to Moses. Whatever might be the historical accuracy of this overall tale, this is an important fact to know, as the experience of the Hebrew people in the desert was pivotal for their self-identity. This would remain a continuing motif throughout their scriptures as well as in the Christian scriptures as well, which would present Jesus as a kind of second Moses.

To most people, Thales is known for two things. On the one hand, he is known for his position that all things are made up of water. This thesis was an honest attempt to explain experience by experience alone. Water is involved in many things and processes, so it seemed to him to be a good candidate for what makes up everything in the world—letting one thing change into another.

He is also known for the story of how he was laughed at when he fell into a well. He is presented like this in the Theaetetus of Plato. This makes him seem like an airy philosopher, who was staring at the stars without any awareness of his surroundings—"with his head in the clouds." In his Politics, Aristotle does tell at tale about how Thales put his knowledge to use to make a profit, so as to prove to the unbelieving that philosophy can be useful if need be. Be that as it may, the story from the Theaetetus is perhaps the best known story about Thales.

In the course of the discussions of the Republic, Plato uses the Allegory of the Cave to explain the nature of education (at least as he believes it is). The general idea is that education is a matter of conversion, turning the soul from false images to the actual reality of the truth. The Allegory tells the tale of prisoners, locked up in an underground cave, unable to move their heads, looking at shadows projected on the wall by others. They learn how to guess about the shadows but never even realize that they are just the projections of objects on sticks. 

Then, someone (i.e. a philosopher) comes along and turns a prisoner around, taking of his shackles. Forcefully, the philosopher shows that person that he has not been experiencing reality but instead has only been looking at shadows. He drags that person out of the cave so as show him what things really are. (Hence, the Allegory proposes that the philosopher teaches him about the way to see the ultimate truths of reality.)

Augustine's Confessions follows the life of the author from his birth through thirteen separate books. Primarily the story of Augustine's early spiritual and educational life and his eventual conversion to Christianity, the book nonetheless covers the important details of Augustine's life. This makes the Confessions one of the earliest examples of an autobiography.