We scientists like to think that information follows from the observations upwards through various intermediate steps to the theories we use to describe, predict, and control our world. Our ideas are determined by our observations; our observations are not determined by our ideas. If there is a disagreement between our observations and our ideas, the ideas must change, not the observations.
This isn’t entirely the case. Our ideas can also influence our observations. What we see is influenced by what we think exists. I will present one example of how our observations are influenced by our ideas.
Prerequisites: None.
Originally Written: January 2019.
Confidence Level: My example of a well established idea in the philosophy of science.
Consider a picture of rapids in a river. Can you tell which direction that the river is going? What sorts of things do you see in the river?
To someone not familiar with whitewater, the most obvious things in this river are rocks, waves, and white. Here is how the river looks to her:
Whitewater rafting / canoeing / kayaking requires being able to quickly gather information and make decisions about how you are going to run the rapid. People who are experienced with whitewater have developed their own terminology to help them parse what they see more rapidly. The terminology describes things that you expect to see in the river. It tells you what exists.
If we have different ideas of what exists in rapids, what we see when we look at a river changes.
A “tongue” in a river is a region of smooth water. It forms the shape of a ‘V’. The broad end of the ‘V’ is upstream and the narrow end is downstream. Most of the water in the river flows through the tongue. A tongue is almost always the easiest way through a rapid.
A “wavetrain” typically follows a tongue. It is a sequence of standing waves. The largest waves are towards the upstream side of the wavetrain and the waves get smaller as you go downstream. Although the waves in a wavetrain might be large enough to dump water on you or even flip your boat if you hit them at the wrong angle, wavetrains are not dangerous. You don’t have to worry about hitting rocks or being pulled under while you are in the wavetrain.
Go back and look at the rapids in Figure 1 again. Can you tell which direction that the river is going? What sorts of things do you now see in the river?
The most obvious things in this river, to someone who is familiar with whitewater, are a tongue and a wavetrain. These features tell her how to run this rapid. She may not even notice the exact locations of the rocks because they are in a region that she has already decided not to go through.
The drawing in Figure 3 contains less information than the drawing in Figure 2. However, it is more useful for someone who is whitewater rafting. Only a few features of the river are identified, but those are the only features that you need.
Our observations of the world are laded with theory. What we expect to exist influences what we see. Some of the theories that we use give more useful results in some situations than others. But the observations cannot be pure arbitrators of the theories that we use to describe them.