Pluto and the Principle of Universality

You will occasionally hear elder Millennials opine to their beheadphoned offspring: "When I was your age, Pluto was a planet!"

Pluto being declassified as a planet was, alongside the simultaneous release of Blur/Oasis singles, one of the defining moments for our microgeneration. 

The body responsible for classifying planets is the International Astronomical Union and you probably don't need to be reminded that they downgraded Pluto from full planetary status to the lesser category of 'dwarf planet' on the 24th August 2006 at their international Congress in Prague.

That was 20 years ago this summer. In that time, Pluto has completed an 8% arc of its journey around the Sun. 

One understated reason for Pluto's declassification is the Principle of Universality. This is the principle that, broadly speaking, states that if a label is truthfully applied to an item t with qualities x, y and z, then it should apply to all items with qualities x, y and z.

The problem was that Pluto shared qualities of size, shape, constitution, orbital proclivities and so on, with an increasing number of objects being discovered in and around the Kuiper Belt. By the Principle of Universality, if Pluto was correctly labelled 'planet' then these objects would rightly be considered planets, too. And then we would have potentially dozens of planets. 

The IAU rejected this option in favour of reclassifying Pluto and its new bedfellows as dwarf planets. 

At various points people suggested just treating Pluto as a special case. But the IAU decided that taxanomic integrity was more important than the grandfather legacy of Pluto.

Like many principles (even non-universal ones) he Principle of Universality pops up all over the placeI was reminded of it when thinking about the UK government proposal for early-release of prisoners.

Prisons are overcrowded. We want to keep sending people to prison, but we don't want to build any expensive prisons. So, we select a category of prisoner for early release.

Let's say everyone who was sent down for 10 years (out in five) will be released after three years instead. Hooray! Problem solved! Lots of freed up cellspace.

But, oh no! Media finds a pair of horrible police-killers (convicted of manslaughter) among the cohort assigned for release. Justice secretary is now assigned the problem of keeping these individuals in prison and still releasing the rest.

Enjoy your summer holiday, Alex Norris! This is not a simple Pluto style problem of recategorisation. 

The crime of killing an emergency services worker has already been recategorised. But in the UK, we are not in the habit (for now) of redefining people's guilty sentences due to changes in law that occur after their sentencing. This legal principle is enshrined in international laws that it used to be a given that the UK would uphold.

What's strongest out of prison walls, the Principle of Universality, and Article 7 of the ECHR? Something's got to give. And the stakes are almost as high as that time Blur decided to release Country House the same week as Oasis' Roll With It.