Now it seems to me […] that refinement and strength of consciousness always stands in proportion to the capacity for communication of a human being (or animal), capacity for communication in turn in proportion to need for communication […] Supposing this observation to be correct, I may then go on to conjecture that consciousness evolved at all only under the pressure of need for communication – that it was from the very first necessary and useful only between man and man (between commanders and obeyers in particular) and also evolved only in proportion to the degree of this usefulness.
