Theories Are Explanations, Not Predictions

There's another example from science like this. On a heat source, put a beaker of water, then put a thermometer into that water and turn on your heat source. Then record, as the time passes, what the temperature of the water is. You will notice that the temperature of the water will increase. You can do this with a saucepan at home, so long as the heat source is relatively constant, the temperature rise will be relatively constant as well.

So after one minute, the temperature might go from 20 degrees Celsius to 30 degrees Celsius. Imagine every minute it climbs by another 10 degrees Celsius. But at some point, it's going to stall when it hits the boiling point, precisely. Now, if you're a thoroughgoing inductivist or even a Bayesian reasoner, and you don't know anything about the boiling temperature and what phenomena happen at that temperature, you can join all of those lovely lines into a perfectly diagonal straight line and extrapolate off into infinity.

After two hours, according to your Bayesian reasoning, according to your induction, we should assume that the temperature of that water will be a thousand degrees Celsius. But of course, this is completely false. What actually happens is once it starts boiling, it stays at its boiling temperature. We get a plateau, and this plateau of temperature, about 100 degrees Celsius, remains there until all the water boils away.

Now, there's no possible way of knowing this without first doing the experiment or having already guessed via some explanatory means what was going to happen. No method of recording all of these data points and extrapolating off into the future could ever have given you the correct answer. The correct answer can only come from creativity.

And notice that science is not about predicting where the trend starts and where the trend goes. In fact, if we want to explain what's going on with the water, we refer to the particles and how, as the temperature increases, the kinetic energy of the particles starts to increase. This means the velocity of the particle starts to increase. Eventually, those particles in the liquid state achieve escape velocity from the rest of the liquid.

At this point, we have boiling. But that escape velocity, the technical term is latent heat, requires energy. And for this reason, we can have heating of something like water without any temperature increase. That's what science is. That whole complicated story about how the particles are moving faster, this invocation of the term latent heat, it's not about trends and predictions; it's about explanation. Only once we have the explanation can we, in fact, make the prediction.