Three windows.

The chairside card I hand out ends with three words: time, space, scale. They are the three windows. Look through the right one while the outcome can still move.

Not the number in the chart. The direction of the numbers, across years. A periodontal chart read once is a snapshot, and every snapshot can be within normal. Read across six visits and ten years, it is a time series, and the trajectory can be screaming while every single visit is defensible. The information was never in the number. It was in the numbers' direction. Write the change, not just the state: 4 to 5, not 5. Four characters, and the record becomes an instrument. Change, not damage, is the primary finding.

Where systems meet. A barrier one cell thick, a bloodstream on the other side of it, a nerve field around both. Things cross. That is the space window at the small end. At the large end there is a corner of a film we already take, where a vessel shows itself once it has started to turn to mineral, and nobody taught most of us to look there. Read the whole film. Every corner, every time. The information was on the image the whole time.

A packet shed by a single bacterium, smaller than a wavelength of light. A city of twenty billion in one mouth. A billion people sleeping badly. The same story runs at every one of those scales, and it looks like a different story at each one. Zoom in until the mechanism shows. Then zoom back out until the person does, because the mechanism was never the point.

None of this needs permission, purchase, or belief in my hypotheses. Put last recall's film beside today's before you walk in. Trend the bleeding as a percentage instead of meeting it fresh each time. Give the person who charts the first two minutes of the visit to say what moved. That is the time window, opened for free.

Next letter: what termites know about disease.

Thad