Week 1: A Sandwich Is a Structure

The opening lecture — what the course treats a sandwich as, why the definition has to be argued for, and what evidence will mean here

22 February 2027

The first sixty minutes. It sets up the proposition the semester tests, and it sets up the standard of evidence the semester marks against.

What the course claims#

A sandwich is a temporary structure whose failure is eaten. That sentence is doing three things: it asserts that the assembly carries load, that its condition changes over time, and that the usual evidence of its failure is destroyed before anyone examines it.

Each of the three has a consequence. Because it carries load, it has a load path worth drawing. Because it changes, a record needs a time on it. And because the evidence is normally destroyed, this course photographs, dimensions and annotates specimens that a diner would simply eat.

Why the definition is the first problem#

Every criterion you might use to decide what counts draws its boundary somewhere inconvenient — enclosure excludes the open-faced assembly, a count of outer layers excludes the wrap, and use admits things nothing else does.

The lecture does not settle this. It establishes that a criterion has to be stated before a classification means anything, because the criterion decides which failures are visible at all. A definition that excludes the wrap cannot describe how a wrap fails.

What evidence will mean#

Three categories, kept apart from the first week to the last: what was observed, what is inferred from it, and what remains unknown. Most of the marks in this course are for keeping the three in their own columns.

Week 1’s own activity is a classification field note, and the Sandwich Field Log is built from four of them.