On The Necessity Of Metaphysics

In other words, it is quite possible that actual existence may be an active force and an efficient cause of observable effects in those things of which we say that they are. If such were the case, all philosophies based upon an existenceless notion of being would be courting disaster, and eventually meet it. It would not take more than two or three disastrous experiments of that kind to convince philosophers that it does not pay to posit being as the first principle of metaphysical knowledge. Hence their repeated attempts to replace it by any one of its many possible surrogates, at the risk of multiplying philosophical failures, so to speak, ad infinitum.

- Étienne Gilson, Being and Some Philosophers. 2nd Ed. Toronto: Pontifical Institute of Medieval Studies, 1952.