What do scientists mean when they say that something exists? Every time I give a public lecture, someone will come and inform me that black holes don’t exist, or quarks don’t exist, or time doesn’t exist. Last time someone asked me “Do you really believe that gravitational waves exist?”
Sabine is a theoretical physicists who had gained prominence (and notoriety) through her book Lost in Math, about groupthink in high-energy physics.
In this post she sums up beautifully what I and many physicists believe, and is vehemently opposed by the prevailing realist crowd here on LW. A few excerpts:
Look, I am a scientist. Scientists don’t deal with beliefs. They deal with data and hypotheses. Science is about knowledge and facts, not about beliefs.
We use this mathematics to make predictions. The predictions agree with measurements. That is what we mean when we say “quarks exist”: We mean that the predictions obtained with the hypothesis agrees with observations.
Now, you may complain that this is not what you mean by “existence”. You may insist that you want to know whether it is “real” or “true”. I do not know what it means for something to be “real” or “true.” You will have to consult a philosopher on that. They will offer you a variety of options, that you may or may not find plausible.
A lot of scientists, for example, subscribe knowingly or unknowingly to a philosophy called “realism” which means that they believe a successful theory is not merely a tool to obtain predictions, but that its elements have an additional property that you can call “true” or “real”. I am loosely speaking here, because there several variants of realism. But they have in common that the elements of the theory are more than just tools.
And this is all well and fine, but realism is a philosophy. It’s a belief system, and science does not tell you whether it is correct.
Here is a homework assignment: Do you think that I exist? And what do you even mean by that?