"There is much more to Mercury than is usually taught in astrological textbooks. Mercury is said to be the symbol of the mind; but this term "mind" covers a multitude of mysteries, and Mercury can be seen to represent a variety of processes and functions in the personality, especially as the latter is developing beyond the normal range of activities familiar to the average cultured individual of our day and age.
If we look at the solar system from a heliocentric point of view, Mercury is seen as the first planet revolving around the sun. It thus can be said to refer to the primary differentiation of the undifferentiated solar energy radiating through space. As such Mercury represents the bi-polar electrical force which is the very substance of all organic activity. This Mercury-electricity is the "tone" of life sustaining and ever renewing the organism isolated by birth as an independently functioning unit, foundation for an individual personality. This "tone" (individualized Solar power) is the involutionary expression of Mercury, and it is said to be focused at the center of the cross formed by the human spine and the line of the extended arms. It represents the power-aspect of Mercury."