In every scientific discovery, we can distinguish at least two aspects: first, the precise course of the discovery with all details and in all its individuality; second, its final result, abstracted from all circumstances and subjective considerations connected with the personal characteristics of the discoverer and the circumstances under which the discovery was made. In this "purified view" the substance of the discovery usually enters into science and establishes itself there in the quality of ascertained truth. Because of this, in the great majority of cases, the history of science does not present information about the specific path that a particular discovery followed; but even if it preserves this information, it is usually only in the form of anecdotes that have come down to us, or fragments about some one moment of the whole discovery, which possibly did not play a decisive role, but was preserved thanks to simple chance.