The modern philosophers - one and all, unless Schelling be an exception - recognize but one mode of being, the being of an individual thing or fact, the being which consists in the object’s crowding out a place for itself in the universe, so to speak, and reacting by brute force of fact, against all other things. I call that Existence.
http://www.commens.org/dictionary/entry/quote-lowell-lectures-some-topics-logic-bearing-questions-now-vexed-lecture-iii-r-5