The rare attempts to do this that have been made have failed from one or other of two causes: they have either been written with a controversial aim and therefore have given only the higher lights or darker shades of the picture, or they have been mere summaries of the larger works, mingling what is relevant and what is not relevant from the developmental point of view. The design which occurs to me is to write a study of the Papacy by taking a score of the outstanding Popes--which means, in effect, a score of the more significant or critical stages in the development of the Papacy--and giving an adequate account of the work and personality of each. The evolution of the Papacy has not, like the evolution of life in general, been continuous. It has had periods of stagnation and moments of rapid progress or decay. Of the first hundred Popes, scarcely a dozen contributed materially to the making of the Papacy: the others maintained or marred the work of the great Popes. It is the same with the environment of the Papacy, which has influenced its fortunes as profoundly as changes of environment have affected the advance of terrestrial life. There have been long drowsy summers closed by something like ice ages; there have been convulsions and strange invasions, stimulating advance by their stem and exacting pressure. I propose to select these more significant periods or personalities of Papal history, and trust that the resultant view of the Papacy will have interest and usefulness. The periods which lie between the various Pontificates which I select will be compressed into a brief account of their essential characters and more prominent representatives, so that the work will form a continuous study of the Papacy. In the selection of a score of Popes out of more than two hundred and fifty there is room for difference of judgment. The principle on which I have proceeded is plain from the general aim I have indicated. The story of the Papacy may fitly be divided into two parts: a period of making and a period of unmaking. Taking the terms somewhat liberally, one may say that the first period reaches from the second to the fourteenth century, and that the subsequent centuries have witnessed an increasing loss of authority, especially in the catastrophic movements (from the Papal point of view) of the sixteenth and the nineteenth centuries. A selection of significant Popes must, therefore, include the great makers of the Papacy, the men whose vice or incompetence brought destructive criticism upon it, and the men who have, with varying fortune, sought to defend it against the inroads of that criticism during the last four centuries. One must make a selection neither of good Popes nor bad Popes, but of the Popes who, in either direction, chiefly influenced the fortunes of the institution; and, in order that no important phase may be omitted, a few men of no very pronounced personality must be included.