How do realists connect experiments with beliefs about unobservable causes?

Scientific realists argue that the success of scientific theories—such as the ability to predict experimental outcomes with extraordinary accuracy—is best explained by the fact that these theories are at least approximately true descriptions of reality.12

Rather than viewing theories merely as instruments for generating predictions, realists contend that scientific practice commits us to the existence of unobservable entities. They connect experiments to these unobservable causes through several key lines of reasoning:31

• Explanatory Power: Realists argue that one cannot make sense of theoretical explanations without recognizing the reality of unobservable entities, such as electrons or chemical bonds.3
• Convergence of Evidence: As noted by Wesley Salmon, when multiple, independent experimental methods yield the same values for theoretical quantities, it would be an extraordinary coincidence if those unobservable entities did not exist.2
• The "No Miracles" Argument: Realists maintain that the systematic success of science across broad domains would be a miracle if the underlying theories were not true. They assert that the most credible explanation for this success is that the world behaves as it does because our theories accurately describe its unobservable structure.12

Ultimately, realists often reject the sharp distinction between observable and unobservable, noting that the boundary shifts with technological advancement.12