"A purely mental life may be destructive if it leads us to substitute thought for life and ideas for actions. The activity proper to man is not purely mental because man is not just a disembodied mind. Our destiny is to live out what we think, because unless we live what we know, we do not even know it. It is only by making our knowledge part of ourselves, through action, that we enter into the reality that is signified by our concepts.
To live as a rational animal does not mean to think as a man and to live as an animal. We must both think and live as men. Illusion to try to live as if the two abstract parts of our being (rationality and animality) existed separately in fact as two different concrete realities. We are one, body and soul, and unless we live as a unity we must die.
Living is not thinking. Thought is formed and guided by objective reality outside us. Living is the constant adjustment of thought to life and life to thought in such a way that we are always growing, always experiencing new things in the old and old things in the new. Thus life is always new."
~ Thomas Merton, from Thougts in Solitude