There is no name in the annals of science which has been the occasion of so long and fierce a controversy as that of Galileo. The historian, the astronomer, and the theologian have all had a share in it. Sometimes there has been a pause in the strife, and the question has been allowed to rest; but after a while another disputant has rekindled the embers, and the struggle has recommenced. This has been the case within the last few years, some writers of considerable ability having appealed to the history of Galileo in order to give point to opinions that they wished to advance. During all this time, if there has been unfairness on one side, there have been injudicious zeal and inaccuracy on the other.

These circumstances must form my apology for interfering in a dispute already so prolonged and so envenomed; and it has appeared to me that I may without presumption hope to amend the errors to which I have just alluded, if in no other way, at least by stating correctly the facts of the case. I do not, however, undertake to write a full biography of the great philosopher, or to give a detailed account of his numerous contributions to the scientific literature of his day; I confine myself principally to those great crises in his life which have given rise to so much discussion, and which have chiefly contributed to make him a name in history.