I use the word 'cause' in the sense in which the moon is the cause of an eclipse of the sun, or in which fatigue is a 'sign' of fever; in the sense in which the entrance of a star into the shadow is a sign of the eclipse, or roughness of the tongue of fever; while by 'coincidence' I mean, for example, the occurrence of an eclipse of the sun while some one is taking a walk; for the.