the wish is father to the thought we believe a thing because we wish it to be true.
☞ This expression is used by Shakespeare in 2 Henry IV: 'Thy wish was father, Harry, to that thought'. However, observations on this kind of self-delusion are found in much earlier writings, including those of Julius Caesar and Demosthenes.
1980Alice Thomas EllisThe Birds of the Air Somewhere in that area of the human mind where the wish is father to the thought activity was taking place. Hunter, Barbara decided, had wangled this invitation in order to be with her.