This is evidently an advantage. But now a difficulty presents itself. When employing these general terms, such as vegetable, animal, the human race, we are speaking of things of which we are ignorant, and are therefore for us as if they had no existence. We cannot have a complete knowledge of vegetables since that word comprehends all plants and trees on the earth; neither of animals, since “animal” includes not only all beasts lacking reason but also man who is endowed with it. We are equally ignorant of the human race, since it is composed of all human creatures, past, present and to come. It is evident that we only know individual persons and things, such as this fir tree or that oak, this horse, this cow, Paul or James, and we know them because we are in a position to distinguish them by naming them, or indicating them.
How is it that philosophers of the mental calibre possessed by Locke, Hume and Berkeley--whose minds follow so closely the progress of the perception of general ideas--did not question how it was that terms which were applicable to these ideas could equally well be applied to particular things? What was the origin of the word _man_ that it could be as suitable for Paul or James as for many men, in fact the whole human race? This is a fact about which philosophers do not appear to have troubled themselves, and which the science of language alone can explain.
In the time of our primitive ancestors human knowledge was evolved gradually from what was confused and vague, before arriving at what was deemed settled and distinct. Man’s vocabulary was small, substantives were rare; that which we now understand by garden, courtyard, field, habitation, was merged into one and the same conception, and would be expressed by one vocable, of which the modern equivalent is enclosure; the word _serpent_ designated all creatures that crawled, the word _fruit_ implied all that could be eaten, the word _man_ all who could think; each name was a general term expressive of a general idea.
We may remember that the Sanscrit word _sar_, to run, which was at first used for rivers in general, became a particular name; a demonstrative element joined to the verb, changing it into _sarit_, run here, sufficed at once to turn it into an intelligible phrase, and the name of a particular river. In order to form the word _man-u-s_, man, the constructors of language combined the root _man_, measurer, thinker, in its secondary form _man-u_, with the suffix _s_, which gives the meaning think-here. This was at first not of general application, but as it could be repeated any number of times and referred each time to different persons, who could each be named thinker-here, it became a general term. We thus see that the name _manus_ was from the beginning something more than a mere conventional sign applied to a particular person as are all proper names. It was a predicative name, that is applicable to all possessing the same attributes, viz., of being able to think, and capable of the same act, that of thinking.