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# Pluto and the Platypus: An Odd Ball and an Odd Duck: On Classificatory Norms

## Details

**Authors** Slater, Matthew H.

**Year** 2017

**Publisher** Studies in History and Philosophy of Science Part A

**Kind of work** article

**Discipline** Philosophy

**Secondary disciplines** Astronomy

**Applied** false

[Read it at the publisher](https://doi.org/10.1016/j.shpsa.2017.01.001) 
10.1016/j.shpsa.2017.01.001

## In authors' words

### What they set out to do (purpose)

To dispute the view that Pluto has been shown not to be a planet, and to examine the norms built into classification.

### Who or what was studied (sample)

Case studies: Pluto and the planets; the platypus in biological classification.

### How they did it (methods)

Philosophical argument by analogy between the two classification disputes.

### What they found (results)

The discovery of other Pluto-sized bodies does not by itself justify excluding Pluto; absent independent reason to exclude the new objects, it supports counting them as planets. Classificatory practice carries normative commitments, which bears on monism versus pluralism about classification.

## Commentary

### In short

The paper argues that finding more Pluto-like bodies does not show Pluto is not a planet, and that where classes are drawn reflects normative commitments as well as observations.

### Response

The paper is about where a category boundary is drawn and why, so distinction is central. The claim that classification depends on norms gestures at perspective, but the author frames it as normativity rather than vantage point, so P is not ticked. Philosophy of science rather than astronomy by the authors' department. Abstract page only.

**Patterns it shows** D

Shows the structure is there

**Added** 2026-10-22

**How to cite this** Slater, Matthew H. (2017). Pluto and the Platypus: An Odd Ball and an Odd Duck: On Classificatory Norms. Studies in History and Philosophy of Science Part A.