Future goods: a purported present sale becomes an agreement to sell, conditioning rights on later acquisition of the goods. Section 6 distinguishes existing goods (owned or possessed by the seller) from future goods and permits contracts for goods the seller has yet to acquire, including acquisition contingent on uncertain events. A purported present sale of future goods operates not as an immediate sale but as an agreement to sell, making performance contingent on the later acquisition or coming into existence of the goods.