…is another’s modus tollens.

[W]hen I was nine years old, I came down with scarlet fever. […] During that year there was nothing in the world which I wanted so much as a bicycle. My father assured me that when I got well I would get one but, childlike, I interpreted this as meaning that I was not going to get well.

Julia Robinson, in: Constance Reid, The Autobiography of Julia Robinson. The College Mathematics Journal, Vol. 17, No. 1, (1986), pp. 3-21