It is of especial interest to the nature-mystic to find that Anaximenes was faithful to the doctrine that the primary substance must contain in itself the cause of its own motion. And the interest is intensified in view of the fact that his insistence on the life-giving properties of air rests on a widely spread group of animistic notions which have exercised an extraordinary influence on the world at large. Let Tylor furnish a summary. "Hebrew shows _nephesh_, 'breath,' passing into all the meanings of life, soul, mind, animal, while _ruach_ and _neshamah_ make the like transition from 'breath' to 'spirit'; and to these the Arabic _nefs_ and _ruh_ correspond. The same is the history of the Sanskrit atman and prana, of Greek _psyche_ and _pneuma_, of Latin _anima, animus, spiritus_. So Slavonic _duch_ has developed the meaning of 'breath' into that of 'soul' or 'spirit'; and the dialects of the gypsies have this word _duk_ with the meanings of 'breath, spirit, ghost,' whether these pariahs brought the word from India as part of their inheritance of Aryan speech, or whether they adopted it in their migration across Slavonic lands. German _geist_ and English _ghost_, too, may possibly have the same original sense of breath." How marvellously significant this ascent from the perceptions of wind and breath to what we now understand by soul and spirit! The most attenuated concepts have their basis in the physical world. Even to this present day, as Max Müller remarks, "the soul or the spirit remains a breath, an airy breath, for this is the least material image of the soul which they can conceive."