Reason is the intellectual capability of humans to confront life's mysteries and, by adhering to the scientific method, to uncover their solutions. Throughout human history, the process of reasoning has greatly expanded our understanding of the Universe, including the structure and function of our own species. Of course, as our knowledge continues to advance and as our scientific tools become even more sophisticated, our current level of understanding will, eventually, come to be viewed as primitive.
Some aspects of human life, such as art and music are conduits for the expression of emotion and, despite their importance in our lives, are not governed by reason. Religion and mysticism, long ingrained in human culture, are not based on reason and, in fact, are threatened by man's intellectual curiosity; the more we understand about our Universe, the less influential these philosophies become. Of course, some argue that religion explores truths that man is not equipped to comprehend; then again, most of these belief systems predate the scientific era.
Reason is man's natural, intellectual process for interpreting his environment. To ignore its power, or to dilute it with mysticism, is to deny the capabilities of our species. Perhaps we must evolve to the next stage before we accept that fact.