Aristotle then moves to the question of property in general, arguing that the acquisition of property does not form a part of household management ("oikonomike") and criticizing those who take it too seriously. It is necessary, but that does not make it a part of household management any more than it makes medicine a part of household management just because health is necessary. He criticizes income based upon trade and upon interest, saying that those who become avaricious do so because they forget that money merely symbolizes wealth without being wealth and "contrary to nature" on interest because it increases by itself not through exchange.