Decidability 2

In my first post on Decidability, I wrote about the Halting problem and how everyday life decisions seem undecidable. Still, we are deciding many things, from minute to minute, from hour to hour, that shape our life, surroundings, and possibly the future. But: Do we decide in the first place or is it arbitrariness? Does it matter which one it is? And if it is not arbitrary, how can we decide?


Only those questions that are in principle undecidable, we can decide.

Heinz von Foerster, Ethics and Second-order Cybernetics

Some time ago, I would have said that decisions are guided and derived from environmental data. The deciding person merges and weights the available data to arrive at a conclusion on how to decide. However, this model has flaws: If the data would lead to a clear answer, there would be no need to decide in the first place; the data just gives the answer. Consequently, only if the data is insufficient to derive a clear answer, the need to really decide arises. Thus, decisions also always result in uncertainty; inherently, we are deciding only the things where the outcome is unclear. Also, in most cases it is an arbitrary choice which data is considered and how it is weighted; infinitely many and equally reasonable decisions are always available – the decision itself is arbitrary.


If you can’t decide between two options, throw a coin. Before it touches the ground you will know which side you want it to land on: Decision made.

My best friend; around when we were in 6th grade

I always liked the idea of this approach to decisions. While in essence it’s not very spectacular, this proposed trick addresses the time component of decisions: If a decision is difficult, we tend to postpone it to an uncertain moment in the future in the hope for more data (or that someone else decides for us). Throwing the coin makes the decision pressing and imminent; and, if, the correct decision cannot be induced by data but is arbitrary, this trick lets us make a decision right now. And this decision comes down to the gut feeling of the deciding person, but it doesn’t matter because the decision is arbitrary whatsoever. My version, by now, is simpler: ‘If you can’t decide between two options, throw a coin and take the option it selects.’


Draw a distinction.

Georg Spencer Brown, Laws of Form

Thus, the coin method is congruent to the proposed mark or cross by G. S. Brown as used by Luhmann: There is no way to decide correctly. You never know the outcome, otherwise there would be no need to decide. The only thing that matters is that you decide in the first place.

Thanks to input from my dad. This post probably deserves a re-write as soon as I have more time to properly study the provided material. Since I decided that all posts also have pictures, I chose some older ones from a vacation last year in Sächsische Schweiz. Back then, I still had borrowed his camera and had even less knowledge about photography than now…

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