When nature speaks to man through his senses, something occurs exactly analogous to the process when man communicates with man through the spoken word. In both cases the perception, that is, the result of the process of perception, is something quite other than the sum of sensations underlying it. Per-ceiving by means of the senses is none other than a re-ceiving of nature's language; and this language, just like human language, bears two entirely different elements within it. According as one or the other element prevails in man's intercourse with nature, this intercourse will be either 'natural' or 'artificial' - to use the terms by which Reid distinguished the two stages of human speech.