The Challenge and Necessity of a Shared Reality

All animals, including humans, have limitations in how they find out about the world. And we humans invent instrumentation to correct for weaknesses in our perceptions of the world. The most basic weakness we have is that our perceptions don’t tell us everything about what’s going on with the world. So we need corrective devices. Some of us need spectacles. To see very distant things, like distant galaxies or planets, we use telescopes; to see very small things, like cells, we use microscopes. It’s hard for many of us to hear the difference between a single tone and a chord, so sound analyzers let us break down complex sounds into their constituents, in a way most of us couldn’t do unaided. We usually see daylight as undifferentiated white light: it takes the prisms to let us analyze the complexity of daylight, to see that it is made up of rays of different colors.

But the acceptance of the instruments we use in analyzing our surroundings is hard-​won. Consider electricity. To find out about electrical currents, we use various measuring instruments—voltmeters, ammeters, and so on. These instruments tend to be familiar, so nowadays we take it for granted that the instrument does what it says on the tin. “It says ‘voltmeter,’ so I guess it’s measuring volts,” we say. But this raises a tricky puzzle about instruments: Since each instrument represents our best attempt to measure what’s true about some aspect of the world, what can we compare its results to? Can we ever really know whether our whole system of knowledge is solid?

One answer to this conundrum can be seen metaphorically in the story of Kon-Tiki. When adventurer and ethnographer Thor Heyerdahl took his balsa raft, the Kon-Tiki, on its trip from Peru to Polynesia in 1947, his crew predicted that the balsa logs from which the raft was built could become waterlogged on the journey. So they took with them spare balsa logs. That way, if any one of the logs from which the raft was built became waterlogged, and so unusable for flotation, they could strip it out and replace it with one of the fresh logs stored on board. But what they couldn’t do, of course, was to strip out and replace all the logs simultaneously. The moment they stripped out a number of logs, the whole raft would collapse, and they would drown.

This image of the raft works quite well as a metaphor for the crisscrossing pattern of justification that we use to demonstrate that an instrument, like the telescope, works and is giving us the information we are counting on it to give us. Suppose you tried to suspend belief in everything: You don’t accept anything at all of current knowledge, and then try to reconstruct all that we do from scratch. That means throwing out everything from knowing how to tell if someone’s illness can be cured by antibiotics, to knowing whether spots mean measles, to knowing the patterns of movement in the night sky, and then justifying all that we believe from scratch, including, for example, which vaccines will work on which diseases. That would be like throwing away all our logs to rebuild the raft from the beginning: We wouldn’t be left with enough to work with. We would drown.

What we can do, however, is test each proposition individually, while keeping steady most of the background, and toss out and replace ideas that don’t pass muster. Given most of our current background of medical knowledge, for example, we can go back and review whether a particular vaccine is really protecting against a particular illness. And similarly, for each medical proposition we believe, we can, holding the rest of the background constant, review and assess whether it’s right.

The raft metaphor also captures another key issue. Each element of our scientific understanding, each log in the raft, only gets its strength by relying on all of the other scientific-​element logs that it is connected to. We trust one bit of science because there are many other bits that, together, support it. In this sense, we are “triangulating”—using several different pieces of evidence together, each coming at the problem from a different angle and testing a different concern, to trust any other given piece of evidence. That is how the scientific raft functions.

Practical instruments that extend what we can perceive with our senses help us identify a common, shared reality out there in the world. After playing with these instruments, we don’t find ourselves saying things like, “Well, maybe LED lights and sunlight behave this way for you, but some other way for me.” We instead tend to use the instrument to reach a shared understanding—and, ideally, to use that understanding to effectively act on the world.

Read More: Science Isn’t Always Perfect—But We Should Still Trust It

We also have to recognize the cases where we do, currently, struggle with our sense of reality. Today, for example, every society across the globe is making decisions that will affect the trajectory of life on Earth for a very long time. But we don’t get immediate feedback on the consequences of those decisions. If we lower carbon dioxide emissions, we can’t “wait to see what happens,” just like we can’t wait to see what happens if we don’t lower emissions. There is so little sense of interactivity with the system; the output is too far into the future. That’s the problem with building our scientific understanding of reality—and also for politics and governments, who are planning policy based on this shared reality.

For an example like this, it’s not that there isn’t any reality out there, but that there are many issues for which the reality is very hard for us to establish. That leaves much room for debate. But science doesn’t give up when the going gets tough. Instead, people have invented further scientific tools and clever experiments that are all aimed at triangulating in on reality to help us deal with the situations where interactivity becomes more difficult. And, ideally, they provide a link to a shared understanding of reality in these more complex cases.

We can’t just go to our corners of the room and pretend that it doesn’t matter if two people or groups are acting on conflicting ideas of how the world actually is. If we are trying to figure out what’s real, and if we need to reach a shared agreement about reality, then we need to proactively find people with a different picture, and work together to help us triangulate on what is truly going on in the world.

Adapted from THIRD MILLENNIUM THINKING by Saul Perlmutter, John Campbell, and Robert MacCoun. Copyright © 2024 by Saul Perlmutter, John Campbell, and Robert MacCoun. Used with permission of Little, Brown Spark, an imprint of Little, Brown and Company. New York, NY. All rights reserved.