of a patient, even the delirium which so affects the bystanders, are less characteristic of fever than the rate of his pulse, and the latter less than the temperature of the armpit or the dryness of the tongue, &c. At every moment the study of science reveals resemblances of facts and contiguities of facts which must be neglected for the sake of others. And if we pass from this profound knowledge of the objects to the empirical knowledge, to the external perception of bodies, it is in immense number that one espies around one traps laid by nature. The sound we hear resembles several others, all produced by different causes; many of our visual sensations likewise lend themselves to the most varied interpretations; by the side of the efficient cause of an event we find a thousand entangled contingencies which appear so important that to disentangle them we are as much perplexed as the savage, who, unable to discriminate between causes and coincidences, returns to drink at the well which has cured him, carefully keeping to the same hour, the same gestures, and the same finery.
The reason of this is that the faculty of similarity and the faculty of contiguity do not give the distinction, necessary as it is, between resemblances and co-existences which are significant and those which are not. The causal nexus between two phenomena is not perceived as
