Logic, in Three Books: Of Thought, of Investigation, and of Knowledge

I. At almost every moment of our waking life our senses are giving rise to various ideas, simultaneous or immediately successive. Among these ideas there are many which have a right thus to meet in our consciousness, because in the reality from which they spring their occasioning causes always accompany or follow one another; others are found together in us merely because, within the external world to whose influence we are accessible, their causes were as a fact simultaneous though not so inwardly connected as to ensure their similar combination in every recurring instance. This mixture of coherent with merely coincident ideas is repeated, according to a law which we derive from self-observation, by the current of memory. As soon as any idea is revivified in consciousness, it reawakens the others which have once accompanied or succeeded it, whether the previous connexion was due to a coherence in the matter of the ideas, or to the mere simultaneity of otherwise unconnected irritants, (it is upon the first fact, the recovery of what is coherent, that our hope of arriving at knowledge is based:) the second, the ease with which coincident elements hang together and push one another into consciousness, is the source of error, beginning with that distraction which hinders our thoughts from following the connexion of things.