Full Idea
The A-theory regards our intuitive distinction of time into past, present and future as objective, and takes seriously the idea that time flows; the B-theory says this just reflects our perspective, like the spatial distinction between here and there.
Gist of Idea
A-theory says past, present, future and flow exist; B-theory says this just reports our perspective
Source
Robin Le Poidevin (Interview with Baggini and Stangroom [2001], p.174)
Book Reference
Baggini,J/Stangroom,J: 'New British Philosophy' [Routledge 2002], p.174
A Reaction
The distinction comes from McTaggart. Physics seems to be built on an objective view of time, and yet Einstein makes time relative. What possible evidence could decide between the two theories?