Here is a link to the text, chapter 9... page 30: http://books.google.com/books?id=gQ...q=einstein&ei=tondSZLWOpnGywTa_pHyDg#PPA30,M1 So I have been analyzing this thought experiment from a causal perspective and have found it to be quite unsatisfactory. The role that lightning plays is key and that is where I will start. How is the experience "it is lightning" possible? Allow me to derive a causal chain in order to illustrate this. First, their must be a material event, an atmospheric discharge of electricity(doe), an emission of light, a subsequent absorption of light by the optical system of the observer, and that data/information is then organized by the mind into the experience(eol). So we have: doe > emission > absorption > eol we can combine the emission and absorption events into a singular causal process so that we have: doe > e/a > eol = a > b > c So the distilled version of this thought experiment is that there are two observers, one located at m', moving with some velocity on the train, and one perpendicular to m, at rest on the embankment. Now at the moment that the embankment observer has the experience "it is lightning", Einstein freezes the action and explains to us that m' naturally coincides with m, and that if the train didn't have the velocity it did, the light emitted from places A & B would be absorbed by the observers optical system at m' in a manner that would allow him experience stroke A & B simultaneously. So the causal chain you must extract from Einstein is: eol > e/a > eol = c > b > c How can the the embankment observer have the experience "it is lightning" before light is emitted from places A & B? Another way of putting it is, does he have the same experience twice?