Turning now to a consideration of the earliest steps which may be said to have cleared the way for the political power of the bishops, we are met by a subject which, though of great interest in itself, is not sufficiently a part of this investigation for us to do more than indicate the lines of its progress. This subject is the development of the practice of giving certain immunities and privileges to churches and monasteries, adopted by the Frankish kings, faithful sons of the church, and then followed by all their royal and imperial successors. In considering the important influence exercised by these immunities on the development of the espiscopal power and the effects of this on the growth of the communes, there are two essential facts which we must always keep prominently in mind. In the first place we must remember that the granting of immunities was a question of privilege to particular individuals or ecclesiastical institutions, and not a universal grant which affected in an equal degree all the dioceses of the realm. This led to the marked differences in rank and importance which existed between the various bishoprics, and in the tenth century, when the temporal power became in many cases an adjunct to the spiritual, caused some bishops to become powerful temporal princes, while others, unable to gain this pre-eminence, remained simply spiritual heads of their respective dioceses. So in the contest between the counts and the bishops we find the latter only victorious in certain cases, and consequently having only certain of the cities under their jurisdiction; a fact which is illustrated as late as the Peace of Constance, where in the ninth article the cities are still divided into episcopal and non-episcopal cities.[88] In the second place we must keep clearly before us an important fact, the truth of which any chronological account of the development of the principle of immunity would easily demonstrate, namely, that with the advance of time and with the growth of that principle, the changes which took place in the different sorts of immunities were not simply those of degree, but essentially and principally those of _kind_.