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We thus require a definition of simultaneity such that this

definition supplies us with the method by means of which, in the

present case, he can decide by experiment whether or not both the

lightning strokes occurred simultaneously. As long as this

requirement is not satisfied, I allow myself to be deceived as a

physicist (and of course the same applies if I am not a

physicist), when I imagine that I am able to attach a meaning to

the statement of simultaneity. (I would ask the reader not to

proceed farther until he is fully convinced on this point.)