Thought experiments and what is probability, anyway?

When I first started going out with my girlfriend I told her about Schrodinger’s cat on one of our earliest dates. She was captivated by the idea. To me that was quite an apt analogy of our relationship at the time. We are friends from back in our undergraduate days. None of us had thought about developing that friendship any further.

So, exploring if we had a deeper connection was a way of finding out if the cat was indeed alive.

For those who don’t know, Schrodinger Cat is a thought experiment. Devised by the late physicist Erwin Schrodinger in 1935 to illustrate a paradox of quantum superposition. It follows, a cat in a sealed box with a poison filled flask. The cat dies when the poison is released.

That’s pretty straightforward. But a proposed interpretation implies that until one looks inside the box, the cat is neither decisively alive nor dead. It only bears possibilities.

In another view, determinateness proposes that all events can be determined completely by previously existing causes. In physics they call this cause and effect. In a deterministic world of casual chains that link time (past, present and future) together, events can be thought of as an inevitable domino like effect of everything that happens.

If that’s true then complete knowledge allows perfect prediction of the future and an impeccable retrace of the past. Pierre-Simon Laplace articulated this thought with almost canonical assumptions and premises of classical mechanics.

The aforementioned views are incompatible. But that’s not to say there’s isn’t any commonality.

In principle, Newtonian mechanics is deterministic. And in practice, dynamic forces of the world amplify interactions by introducing uncertainties in the mix. Quantum mechanics evolved embracing the idea of less than perfect confidence in prediction. That’s saying, we are not able to measure outcomes with perfect prediction. What we can do is calculate the probability of each outcome.

To that, Albert Einstein unsatisfactorily remarked about god not playing dice with the universe.

There are multiple schools of thought on how to approach these matters. And most certainly, the highly revered ones lean on the idea that probability is fundamental.

So, what is probability?