D O C U M E N T 3 3 4 D E C E M B E R 1 9 2 8 3 1 9 The final result is thus . In particular, the equation resulting from a single contraction of this equation should be quite useful for our purposes. Kind regards, your A. Einstein 334. To Chaim Herman Müntz [Berlin,] 13 December 1928 Dear Mr. Müntz, I have had a simple, but bold idea that will throw Hamilton’s principle right overboard. We shall now put the cart before the horse: I will choose the field equa- tions in such a way that I can be certain that they will lead to the Maxwell equa- tions. I start with the identity[1] After contraction in i and m, [2] This is multiplied by and then its divergence with respect to is computed. The result is . Now, in the first term the symbols and are exchanged, likewise the order of dif- ferentiation (this is allowe because of the vanishing of the “curvature”) then this term becomes . Then one combines the first and the third terms to obtain When (field equations), this leads to (Maxwell equations.) i l m . + . +  i   lm . + . +  0  + i l m i lm  i m l + +   i   lm i l  m i m  l + +   0  +   m  lm   m    m +  l   l    l –    l – + 0   l    l –   x -------l -   l x -------- - –  f l = hgl h  l gl    f      h    l gl   – + 0  h  l gl    h  l gl   h    l gl –   f      0  + G   G   0 = f      0 =     l   –    l   