---
title: "PHI403 Lecture 06 — Under Ideal Conditions"
type: source
tags: [philosophy-of-science, idealisation, ceteris-paribus, causal-isolation, cartwright]
authors: [Anjum, Rani Lill; Rocca, Elena]
year: 2023
venue: "PHI403 Causation in Science, NMBU"
kind: handout
raw_path: "raw/Philosophy of Science/PHI302 06 Under Ideal Conditions.pdf"
created: 2026-04-20
updated: 2026-04-20
key_claims:
  - Scientific laws are typically stated with a ceteris paribus clause ("all else being equal") that cannot be fully specified.
  - Cartwright (1983, 1999) and Dupré (1993) argue reality is irreducibly "dappled"; universal exceptionless laws are artefacts of idealisation.
  - Strategies to rescue perfect laws — probabilistic reformulation, causal isolation, exhaustive condition-listing — each have costs.
  - The ceteris paribus clause risks making causal claims vacuously true ("C causes E, unless it doesn't") — unfalsifiable.
---

# PHI403 Lecture 06 — Under Ideal Conditions

Continues the critique of strict regularity by examining the **idealising** moves that make laws look exceptionless. Theoretical physics enjoys frictionless falls, perfect vacua, near-light speeds. But medicine, biology, psychology, and the social sciences almost never see ideal conditions.

**Nancy Cartwright** (*How the Laws of Physics Lie*, 1983; *The Dappled World*, 1999) and **John Dupré** (*The Disorder of Things*, 1993) argue reality is irreducibly messy; imposed order is artificial.

The lecture catalogues strategies for getting laws from irregularities:

- **Probabilistic laws** ("C causes E with probability P") — universal but less useful for prediction.
- **Causal isolation** — build closed systems (lab, thought experiment) to exclude interferers; external validity suffers.
- **Ideal conditions** list — "C causes E under cond₁…condₙ excluding interferers₁…interfₙ" — exhaustive but impossible.
- **Ceteris paribus clause** — "all else being equal"; practical but risks making claims unfalsifiable.

The lecture's punchline: *if the effect is guaranteed only whenever it actually follows, how are we better off than before?* The ceteris paribus clause hides the problem rather than solving it.

## Connections
Back-link: [[sources/2023-anjum-rocca-phi403-causation-in-science]]. Concepts: [[concepts/regularity-theory-of-causation]] · [[concepts/dispositionalism]] · [[concepts/rct-limitations]] (external validity).