January/February 2015

Kant and the Smashing Beer Glass

Written by Patrick Cannon

You get back from the bathroom.

"Two more, please," your friend mouths to the bartender, holding up two fingers. She nods subtly in recognition. You watch as the busy woman reaches for two glasses with one hand, working the cash register with the other. In a moment of inattention, she loses grip of one of the glasses. It smashes as it hits the wooden floor. The shards glisten like toothed diamonds against the dull background.

While this event may seem trivial, a glass falling and hitting the floor actually brings up another interesting topic in metaphysics: causality.

When Kant was only twenty-four, the Scottish philosopher David Hume published his magnum opus, An Enquiry

Concerning Human Understanding (1748). Among other things, Hume was interested in our common sense understanding of causality. We usually think we can know about what's going to happen in the future based on our intuitive knowledge of the laws of nature, that is, how things behave. For example, we know that if we lift up something heavier than air, like a beer glass, and let go of that object, it will definitely fall downwards, and, being glass, may shatter. David Hume, sceptically asked, "How do we know that?"

Hume argued that we often assume that if event B always follows event A, then A caused B. We believe there is a necessary connection, that is, a relationship which can be no other way, between A and B. Strictly speaking though, Hume added, the most we can logically claim is that up until now heavy objects have always fallen downwards. And the only basis for thinking that the same connection will hold ( for example, a cup will subsequently hit the floor when dropped), is our belief that the future will continue to resemble the past. That belief, Hume continued, we gain merely through custom or habit. In other words, Hume was saying that all our ideas about causation are down our own habituation to associated events, and that's it. Thus, the causal connections we make have nothing to do with knowledge of any necessary connection, but rather we derive them from our experience. Strictly speaking, we have no justification for claiming knowledge of causality.

This scepticism about causality freaked Kant out. It was this work by Hume that, Kant tells us, "interrupted my dogmatic slumber" - changing the direction of Kant's philosophy.

As said above, Kant believes that in our experience of the world we use a 'cognitive matrix' to make sense of the stimuli around us. In addition to time and space (which Kant called the forms of sensibility), he posited a complex mental architecture he called the categories of the understanding, which also play their part in bringing forth the phenomenal world. He posited twelve categories in all, including plurality (how many objects there are), existence, and possibility (what does exist; and what, in principle, could exist). The categories basically comprise our cognitive toolbox for making sense of our sense data, and for making judgments about our experiences too. Most relevant to our present discussion is the category of causal dependence, or cause and effect. In other words, for Kant, our perception of the world in terms of cause and effect is something our minds impose on our experience of the world.

Since cause and effect are thus ineradicable features of the mind to Kant, this means causality isn't as uncertain as Hume made it out to be. Just before watching the glass fall and shatter on the floor, Kant would say we could know for certain the glass would fall downwards. How could we know this? Kant tells us that the phenomenal world, the world as we experience it, is governed by deterministic laws. (Kant was very impressed with Newton's three laws of motion.) However, physical laws only apply to the phenomenal world, not the noumenal, Kant argued. So he's saying that physical laws don't say anything about the world in and of itself. In other words, the deterministic physical laws we're familiar with, like the law of gravitation, are only representative of human psychology, or how our minds organise the world for our experience. But given that our minds do organize the world in this way, we can know that we're going to experience the world as being organized in this way.