In our efforts to make knowledge accessible to everyone, if we’re not careful, good intentions can cause us to blunder into useless attempts that benefit no one. I was painfully reminded of this recently when I received a request from a university for an electronic version of my book Show Me the Numbers to accommodate the needs of a student who is blind.

By providing a student who is blind with an electronic version of my book, these well-intentioned folks hoped to make it accessible through the use of “reading software”—software that reads text aloud. I explained to them that books about data visualization cannot be converted into a form that is accessible to someone who is blind because much of the content—indeed, the most essential content—is contained in images that must be seen. They responded by arguing that the Chaffee Amendment gave them the right to convert my book into an accessible form, whether I granted them permission or not, so they would remove the book’s pages from its binding and scan them individually to create an electronic version. When I pointed out that the Chaffee Amendment did not apply in this case because the version of my book that they would create could not possibly be accessible to someone who is blind, they chose to ignore my concern.

I wish I could make the content of my books about data visualization accessible to people who are blind, but I can’t, and technology can’t either. Even if technology existed that could convert a data visualization—an image—into a verbal description, that still wouldn’t solve the problem, for a verbal account of quantitative values in a graph is not a substitute for visual perception. The patterns that are revealed in a data visualization and the operations that are enabled by it (e.g., comparing values and patterns) are not revealed or enabled by words.

Good intentions cease to be good when they produce ineffective results. Sometimes accessibility isn’t possible.