Empirical Evidence - Explanation and examples

Franky Bacon the Science God, armchair reasoning, and a rationalist-empiricist rumble. 


What is empirical evidence?

There was an early debate between the rationalists and empiricists about how we can know what’s true. The rationalists, such as Descartes, Leibniz and Spinoza, had such confidence in their reasoning abilities that they didn’t actually think they needed to collect evidence to ascertain certain truths. Not a terribly humble bunch of grapes.

Tell your mate Descartes, we probably need a bit of both thinking from first principles and a bit of actually gathering evidence - how much depends on the problem we’re looking at.

Those who have handled sciences have been either men of experiment or men of dogmas. The men of experiment are like the ant, they only collect and use; the reasoners resemble spiders, who make cobwebs out of their own substance. But the bee takes a middle course: it gathers its material from the flowers of the garden and of the field, but transforms and digests it by a power of its own. Not unlike this is the true business of philosophy; for it neither relies solely or chiefly on the powers of the mind, nor does it take the matter which it gathers from natural history and mechanical experiments and lay it up in the memory whole, as it finds it, but lays it up in the understanding altered and digested. Therefore from a closer and purer league between these two faculties, the experimental and the rational (such as has never yet been made), much may be hoped.

Francis Bacon (inventor of the scientific method; AKA Franky Boy; AKA God of science

There are some fancy latin words to describe these two competing ways of knowing - a priori and a posteriori - but the concepts are pretty simple. Basically, the rationalists believed that the primary way to get evidence is via a priori reasoning, that is, without (or ‘prior’ to) evidence or experience. The empiricists were proponents of a posteriori reasoning, which is based on observation or evidence.

Examples of empirical evidence

We saw an example of an empirical question in the Overton window entry (albeit a difficult one to answer): if you want to shift the window, should you push for extreme changes or small incremental ones?

Let’s pretend you’re a doctor and you’re interested in lowering blood pressure as a way to reduce the chance that people have heart attacks, and ultimately live better lives. You hear that a drug named atenolol slows down the heart and reduces blood pressure. You’re also aware of the importance of running randomized controlled trials to work out if the drug will actually work, so you run a large trial and determine that atenolol does indeed statistically reduce blood pressure in people who take it compared to a control group that took a placebo. #empiricism, right? Except the problem is that when you include its effect on mortality (i.e. your risk of dying), even though atenolol reduces blood pressure a similar amount to other drugs, it doesn’t reduce your mortality by as much. A priori reasoning might have told you that reducing blood pressure == improving mortality, but a posteriori (or empirically) this isn’t true.

The important lessons to tell the grandkids from your experiments: empiricism is important for getting the right answer, measure important end points and don’t just rely on a proxy (for your discrete internet browsing OR your scientific experiments).

Also check out

  1. Rationalism vs. Empiricism, Stanford Encyclopedia of Philosophy
  2. The Control Group is Out of Control, Scott Alexander

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