The Carillon, October 14, 2010
Radical Skepticism, Part 3 of 4: Kantian Skepticism
Radical skepticism concerning the external world is the philosophical view that we cannot have accurate knowledge about the physical reality that exists outside our minds. If radical skepticism were true, then we could not know the external world. Moreover, if God were to exist, we could not know the external world's revelation of God, whether God's revelation is via the heavens declaring His glory or via Scripture's pages presenting information about Jesus Christ.
Kantian skepticism is inspired by the epistemology (theory of knowledge) of the German philosopher Immanuel Kant (1724-1804).
According to Kant, all our knowledge begins with sensory experience, but the human mind, via its conditioners of sense-experience and its categories of thought, makes a significant contribution to this knowledge. In fact, these conditioners and categories determine for us what we can experience, and they shape this experience. Using Kant’s terminology, all we can perceive is phenomena (what our mind has conditioned and categorized), not noumena (the things themselves).
In effect, our mental conditioners and categories are like rose-tinted glasses. The glasses project pink onto all we see. Similarly, our mental conditioners project space and time onto our experience. Also, via our mind’s category of, say, causality, we project causation onto the events we experience. We project cause onto, say, a pool cue hitting a pool ball, and thereby we “know” that the cue “causes” the ball’s movement. Also, via the mind’s category of substance, we project the notion of material stuff onto what appears to be, say, a brick. We do the same with various other mental categories, such as existence. (According to Kant, there are twelve such categories.)
Better yet, think of our mental conditioners and categories as a meat-grinder/sausage-making machine. The phenomena of experience would be constituted by the ground meat (meat which ultimately is noumenal); what we know—i.e., the phenomena, which are the products of the shaping of the conditioners and categories—would be the sausages; the noumena, what is real, would be (besides the meat that’s been shaped into sausages and is only known as sausages) the stuff that does not fit into the grinder (e.g., the table, meat cutting tools, the butcher, bicycles, suspension bridges, etc.). So, according to this Kantian view of knowledge, no matter how much we grind, we cannot know the external world.
Should we be persuaded by the Kantian version of radical skepticism? I think not, for four reasons.
First, if Kantian skepticism is true, then science’s search for causal connections/laws ultimately is a search for connections/laws not really in the world but in our heads—which is plainly false.
Second, as philosopher Jim Leffel astutely observes: “The success of scientific technology is a strong argument that our perceptions of the world are relatively accurate.” Think of sending rockets to the moon, genetic testing for cancer, laser eye surgery, and the like. Leffel adds: “We couldn’t do these things without an essentially reliable correspondence between our ideas of reality and reality itself.”
Third, for Kantian skeptics to perceive that the mind cannot perceive things as they are requires that the mind can. Apparently, the skeptic can stand outside the meat-grinder/sausage-making machine to tell us about it. But the skeptic should only see sausages, not a meat grinder, meat, etc. Surely, if the skeptic can have this “outside” view, then so can everyone. The view is self-defeating.
[The previous point can be argued more carefully as follows. The Kant-inspired skeptic holds to the thesis that the world is misperceived by humans via their coloured and distorted concepts of it (hereafter, this thesis will be referred to as the Kantian thesis). In other words, the Kantian thesis has to do with a particular aspect of the world: i.e., that humans in fact misperceive the world via their concepts. Significantly—to gain traction—Kantian skepticism must involve an admission that we can know, via our concepts, that the Kantian thesis is true. However, this means that the skeptic presupposes an alternative non-Kantian thesis, a thesis which holds that humans, via their concepts, actually do know the world in a non-coloured, non-distorting way. Now, because this alternative thesis is not self-contradictory (and thus not knocked out of the explanatory competition right at the start); and because the Kantian thesis requires that the alternative thesis is true (albeit with respect to a limited domain); and because there seems to be no overriding reason to limit the domain of the alternative thesis in the way the Kantian thesis does: we can conclude that the doubt cast by the Kantian thesis onto observation is seriously weakened. But this means that it is quite reasonable to accept as accurate the everyday evidence that our observations of the everyday/scientific sort very apparently and very often are accurate.]
Fourth, Kant’s theory of knowledge faces some other deep problems. The categories of the understanding are supposed to apply to phenomena, not noumena. However, the category of causation is applied to noumena (as the cause of the phenomena). Also, the category of existence is applied to noumena too (noumena is said to exist). And so on. In other words, Kant’s view is contradictory in some of its crucial tenets.
Thus, it’s reasonable not to succumb to radical Kant-inspired skepticism. We can know the external world, albeit fallibly and non-exhaustively. Significantly, this opens the door to knowledge of God based on the evidence that the world provides.
Next: Linguistic skepticism.
P.S. The above column is a slightly revised excerpt from my larger article, "Reasonable Skepticism about Radical Skepticism," Christian Research Journal, Volume 31, Number 5 (2008): 30-38.
Apologia columns on radical skepticism:
- Radical Skepticism (Part 1 of 1): Funky/Pop Skepticism
- Radical Skepticism (Part 2 of 4): Sensory Skepticism
- Radical Skepticism (Part 3 of 4): Kantian Skepticism
- Radical Skepticism (Part 4 of 4): Linguistic Skepticism
- Skepticism Concerning Colours?
- Nietzsche's Skepticism
(Hendrik van der Breggen, Ph.D., is assistant professor of philosophy at Providence College, Otterburne, Manitoba, Canada. The views in this column do not always reflect the views of Providence.)