"Matter can be conveniently divided for descriptive purposes into space , time , mass, and energy . However we can only describe any one of these phenomena in terms of the other three. Any definitions we care to make about matter are thus tautological ."

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One of the unfortunate consequences of the intellectualization of man's spiritual life was that the word "spirit" was lost and replaced by mind or intellect, and that the element of vitality which is present in "spirit" was separated and interpreted as an independent biological force. Man was divided into a bloodless intellect and a meaningless vitality. The middle ground between them, the spiritual soul, in which vitality and intentionality are united, was dropped.

— Paul Tillich