While the back-and-forth method has been often attributed to Cantor, it turns out that in the original proof of the characterisation of countable linear dense orders, themapping is constructed in a single#R##N#direction. Cameron has called this method Forth and has shown that it can fail to build an automorphism for some homogeneous structures.We give in this paper a characterisation of those homogeneous structures#R##N#for which Forth always builds an automorphism. This generalises results by Cameron and McLeish.
['Roger Villemaire']
HOMOGENEITY AND FIX-POINTS: GOING FORTH!