A loaf of bread on a steel plate, correctly weighed.
I leave the paintings here and do not come back. From this panel to the end of the series there is no person in the frame, and I want to be clear that this is not a trick of composition. The machine is more truthful without me standing in front of it, and the first thing it does once I am gone is weigh a loaf of bread in the dark.
Caravaggio painted the Supper at Emmaus at the exact instant of recognition. Two men have walked all day beside a stranger and noticed nothing, and then he breaks the bread, and they see. The whole picture is built around that half second. Arms fly out. A chair scrapes back. The bread is at the centre of the table and it is the reason everything else in the painting is moving.
Here is the same loaf on a scale that has established its mass to the gram and knows nothing else about it and never will.
That is the painting. There is no other content in it. The steel is scratched and slightly rusted at the edges where the weighing plate meets the housing. The crust has a good ridge along the top and takes the amber light the way old varnish does. The scale is correct. I want to stress that the scale is correct, because the temptation is to make this a picture about a machine being wrong, and the machine is not wrong. It is exactly right about the only question it is capable of asking.
We built a device that touches bread and learns its weight. Then we put it in every supermarket in the country and left it running through the night.
I called this one the witness because something has to be. There was nobody else in that part of the store. If a thing is going to be present at an event and record what it can of it, then it is a witness, and this is what its testimony looks like: nine hundred and forty grams, no error, next item.