Clostridium botulinum (microscope view) (credit: Wikipedia) 

Another more general example of the dangers posed by an inaccurate picture of reality can be seen in the common activity of home canning. I may think I know all about bacteria and how to can foods at home in sealer jars. If I’ve looked through microscopes, I may be confident my picture of the microscopic level of reality is a true one. But if my knowledge of home canning covers only common bacteria, my knowledge may prove to be a dangerous thing. The usual boiling-water bath for foods canned in jars does kill most bacteria, but for a few microbes, boiling is not enough. Botulism is nothing to be played around with. Botulinum bacteria can be boiled to death, but their extremely deadly toxins can survive boiling. My partial and inadequate set of beliefs about home canning might get me killed.

Or consider a few even more basic examples. Even my senses sometimes are not to be trusted. I may believe that light always travels in straight lines. I may see, half immersed in a stream, a stick that looks bent at the water line, so I believe it to be bent. But when I pull it out, I find that it is straight. If I am a caveman trying to spear fish in a stream, blind adherence to my ideas about light will cause me to starve. I will overshoot the fish every time, while the girl on the other shore, a better learner, cooks her catch.

I can immerse one hand in the snow and keep the other on a hand warmer in my coat pocket. If I then go into a cabin to wash my hands in tepid water, I find that one hand senses the water is cold, the other, that it is warm. Can I not trust my own senses?

When we seek to find some things in our experience that we can believe in absolutely, we are stopped by questions like “What do I really know?” and “How can I be sure of the things that I think I know?” and “Can I even be certain of what I see, hear, and touch?” We are deeply aware that we need a reliable core around which we can build the rest of our belief system or we may, sometime down the road, suddenly find that a whole set of ideas, and the ways of living the system implies, are dangerous illusions.