There is much from the writings of Caesar and his actions pre- and post-Pharsalus that civil war was something he didn't entirely want but maybe that it was something forced upon him by the Senate.

So really despite Caesar symbolically crossing the Rubicon under arms and supposedly stating 'the die is cast' the fact that he sent envoys to Pompey trying to prevent conflict perhaps shows that the real decision to go to war lay with Pompey and the Senate.