One of the hardest classes I ever taught was an introduction to philosophy class called History of Thought. Why was it so difficult? Philosophy, last block of the day (85 minutes), final semester, 25 high school seniors. Plus, I had never taught philosophy.
Fortunately, I was saved by my interest in the subject. While preparing my lessons certain things especially fascinated me like the synthesis of thought created by key thinkers. Of course, just because a synthesis is formed doesn’t mean it is correct, but it does show how human thought progresses. Here are two examples.
Plato’s Two Worlds
Heraclitus of Ephesus (c. 535-475 B.C.) believed that the world was in a constant state of change. Plato quoted him as saying “No man ever steps in the same river twice.”
Parmenides of Elea (c. 500 B.C.) disagreed with Heraclitus. Contrary to what our senses tell us, change is an illusion. Parmenides boldly asserted, “Whatever is, is.” If something truly exists—if it is—it cannot change.
Plato (427-347 B.C.) offered a solution to the philosophical stalemate that had occurred between Heraclitus and Parmenides. He proposed that there are two worlds: a constantly changing world of matter and an unchanging world of Ideas where things exist in their perfect Forms. For instance, in the world of matter, apples change by decaying. But in the world of Ideas a beautiful, perfect and unchanging apple exists, which is source of all apples in the world of matter. In addition, there’s overlap between the two worlds because things in the world of matter are receptacles for the Forms that exist in the world of Ideas. Thus, a physical apple contains the Form or Idea of apple.
Kant’s Mental Categories
Rene Descartes (1596-1650) sought absolute certainty by using reason alone. Why? Because our senses often deceive us. For example, the size of the sun and moon look the same, but they are vastly different in size. And melted and hardened wax look and feel completely different, but they are the same substance. Descartes’ reason-only approach to knowledge is called rationalism and knowledge acquired through reason alone is called a priori.
David Hume (1711-1776) sought absolute certainty by using the senses alone. He believed that everything in our minds comes from sensory experience. Thus, we do not have innate ideas. Rooting all ideas in experience, however, led Hume to skepticism not certainty because our experiences are constantly changing. Hume’s experiential-approach to knowledge is called empiricism and knowledge acquired through experience is called a posteriori.
Immanuel Kant (1724-1804) was awakened from his “dogmatic slumbers” by Hume’s writings. His goal was to find a synthesis between rationalists and empiricists. Kant writes, “That all our knowledge begins with experience there can be no doubt. But although all our knowledge begins with experience, it does not follow that it arises from experience” (Critique of Pure Reason). In other words, the empiricists are making a good point, but they are also missing something. Kant divided the mind into three “faculties”:
- intuition or perception
- understanding
- reason
He then searched for the foundation of each faculty (i.e., that which makes the existence of each faculty possible). Regarding the faculty of perception, he concluded that space and time are the foundation of perception. For example, the statement “The cat is on the mat” depends on the foundation, “Objects exist in space and time.” This shows that space and time in themselves are not a part of external reality; they are part of the structure of the mind. Space and time are the mental glasses we use to view the world.
Regarding the faculty of understanding, Kant concluded that the mind brings innate categories of understanding to reality. These categories are substance, causality, unity, plurality, necessity, possibility, and reality. Kant believed Hume couldn’t find these concepts in the external world because they are a part of the internal world of the mind.
What about the faculty of reason? Although this faculty was supposed to produce “pure” concepts uncontaminated by the senses such as “God” and “soul,” Kant couldn’t find a foundation for it. Of course, Kant’s rationalistic argument didn’t incorporate divine revelation.
According to Kant there are two worlds: the noumenal world or ultimate reality, which includes God, the soul, and the object-in-itself; and the phenomenal world or the world of appearances we experience. The most we can say with certainty about the noumenal world is that it exists because the phenomenal world is ultimately an appearance of something. All we can know for certain are things in the phenomenal world that we experience through the categories of the mind.
Kant’s mental categories were an ingenious solution to a roadblock in thinking. And the idea that we are born with brains that have a particular structure matches with various fields of learning, such as psychology and linguistics.
Human thought often moves forward not by dismissing previous thoughts but by incorporating them in creative ways.
After graduating from Gordon-Conwell Theological Seminary, I served as a high school Bible teacher in Asia. I enjoy traveling, writing, and playing the drums. For a deep dive into church history and the character of God, see my book Surprised by Hell.