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 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.

Thoughts In Solitude (ed. Farrar, Straus and Giroux, 2011) - ISBN: 9781429944076