 Defenders of the argument respond that there is a key similarity between the cosmos and its content, namely, both are contingent. However, why should we think that the cosmos is contingent? Defenders of the view contend that if the components of the universe are contingent, the universe itself is contingent. Russell replies that the move from the contingency of the components of the universe to the contingency of the universe commits the Fallacy of Composition, which mistakenly concludes that since the parts have a certain property, the whole likewise has that property. Hence, whereas we legitimately can ask for the cause of particular things, to require a cause of the universe based on the contingency of its parts is mistaken.