When an individual obtains money by offering something in return, but doesn’t exchange this money for other goods immediately, he generates savings. He has offered more in the market than he has withdrawn from it. He can either keep the money to himself for later consumption, purchase factors of production with it and hence accumulate capital, or make the money available in a credit transaction. In doing so he acts as capitalist. He will only do so if he prefers what he will get in return in the future to what he can obtain with it now. This is determined by his time preference.