The author argues that consciousness and its meaning may only be defined and explained within an ontological system. Such a system is proposed in this article, with matter, energy, and life as its components, and with all its components defined as changes. The systematic relations between matter and energy and the semantic relations among all its components together may define and explain what and how consciousness is, why there is consciousness, where and when it may occur, and what is its (...) significance or meaning. (shrink)