Progressive enhancement and accessibility redux

Josh Fremer being quoted on QuirksBlog on the topic of: "what's the difference between accessibility and progressive enhancement?"

I think of [progressive enhancement and accessibility] as the same process, but with different foci. Accessibility aims to optimize an experience across a spectrum of user capabilities. Progressive enhancement aims to optimize an experience across a spectrum of user agent capabilities...

What is the application of color to a website if not a progressive enhancement targeting user agents that can discern colors? Whether the "agent" in this case is the electronic device in the user's hands or the cells in their eyes is kind of moot. The principles of both PE and accessibility require us to consider the user who is unable to receive color information.

What an interesting idea: user agents being human beings or electronic devices, doesn't matter, it's all about starting with the most basic functionality and enhancing from there.

That’s an interesting concept to think about, especially in light of his Josh's final point:

a fun little thought experiment is to imagine a sci fi future in which users can plug computers directly into their brains, or swap their personalities into different bodies with different capabilities. This further blurs the line between what we traditionally call a "user agent" and a user's innate disabilities. "This web site is best viewed in a body with 20/20 vision and quick reflexes."