Alfred North Whitehead once said that the history of European philosophy was basically a series of footnotes to Plato.  In a similar way, we might say that the history of philosophy for the last two hundred years is one long footnote to Immanuel Kant (1724-1804). We have already discussed the impact of his thinking on the key debates of philosophy. In chapter 4 we met his understanding of knowledge. In chapters 7 and 8 we processed the implications for what we might know about reality.
However, in this section we want to fill in some blanks about how his ideas played out historically in the key thinkers of the last two hundred years, most of whom we have already met at some point in this book. We want to set up the context within which the key players of postmodernism emerged, the thinkers we will discuss in the next section. By the end of the chapter, we want to argue again that a "critical realist" approach to the world is both justifiable and an appropriate Christian understanding (see chap. 8).
Kant, if you recall, was wrestling with the competing claims of rationalism and empiricism. Rationalists argued that truth was a matter of clear thinking and tended to see our senses and experiences as potentially misleading. Empiricists emphasized the importance of our senses in coming to truth. David Hume took empiricism to its most extreme form, showing that ideas we have about thinks like right and wrong or about cause and effect have no real basis in our experience.
Hume woke Kant from his unexamined assumptions about such things. His conclusion, as we have seen, was that the content of our thinking does indeed come from our senses and experiences. But the organization of that content takes place according to certain innate categories in our minds--categories like space and time, cause and effect, and the moral law. As a consequence, we cannot know the world as it actually is in itself (das Ding an sich). We only know the world as our minds organize it.
For Kant, we had good reason to trust the way our minds organized things. God was trustworthy. Many of the philosophers who followed Kant were not so convinced. Some were not so convinced that it made sense even to speak of a "world as it really is" in the first place. Others thought we could know the world as it is by some other means.
Before we organize the thinkers we have in mind, a strong word of caution is in order. One of the "truths" of which postmodernism has reminded us is that organizing specific, concrete people as I am going to do almost always--if not always--involves skew. These thinkers probably were not consistent at every point. They lived at specific places and times--contexts that colored and affected what they said and how they said it. They may have changed their minds on some things over the course of their lives.
In short, categorizations like the following, often called typologies, almost always--if not always--skew reality as it is. Beware of the either-or. Beware of those who set up false alternatives. Beware of "labeling," as we said in chapter 11.
The first thinker we want to consider after Kant is Arthur Schopenhauer (1788-1860), who clearly reflected the influence of Romanticism on his thinking (see chap. 13). If Kant argued that we cannot know the world as it actually is in itself, Schopenhauer believed that we could, just not through our reason. Rather, our "will," the drives and desires in us, give us direct knowledge of the world as it is on an intuitive rather than rational level. There is a pre-thinking, emotional intuition that gives us direct knowledge of the world as it actually is.
We are less likely to have heard of Schopenhauer than some of those he influenced. For example, the psychologists Sigmund Freud and Carl Jung took cues from his sense that our rational minds were directed by the pre-conscious forces of our desires. Further, Schopenhauer believed that the most significant motivation of our lives is our "will to live"--the drive to survive. This idea was a major influence on Friedrich Nietzsche in the late 1800's, who argued that a "will to power" was our most basic drive, a drive to achieve, gain power, and dominate. They then directly and indirectly influenced the existentialists of the 1950's we discussed in chapter 9, who believed that the primary human task is to determine who we are and why we want to continue living.
A second reaction to Kant was that of G. W. F. Hegel, whose theory of history we discussed in the previous chapter...
 Process and Reality (Free Press, 1979), 39.