For Heidegger in "Being and Time" this illustrates, in a very practical way, the way the present-at-hand, as a present in a "now" or a present eternally (as, for example, a scientific law or a Platonic Form), has come to dominate intellectual thought, especially since the Enlightenment. To understand the question of being one must be careful not to fall into this leveling off, or forgetfulness of being, that has come to assail Western thought since Socrates, see the metaphysics of presence.