When you think, you think of something; when you use a name, it must be the name of something. Therefore both thought and language require objects outside themselves. And since you can think of a thing or speak of it at one time as well as another, whatever can be thought of or spoken of must exist at all times. Consequently there can be no change, since change consists in things coming into being or ceasing to be.
The search for something permanent is one of the deepest of the instincts leading men to philosophy. It is derived, no doubt, from love of home and desire for a refuge from danger (...) Philosophers have sought with great persistence, for something not subject to the empire of time.
Yet, certainly, the wise learn many things from their enemies; for caution preserves all things. From a friend you could not learn this, but your foe immediately obliges you to learn it. For example, the states have learned from enemies, and not from friends, to build lofty walls, and to possess ships of war. And this lesson preserves children, house, and possessions.
The present theory then must be considered to be a suggested program or framework for future research and must stand ...