On the other hand the subordination of a multitude of small features to one dominant one enters largely into the design of every good Gothic building; with the result that if the great governing feature or mass has been carried out in its entirety, almost any feature, no matter how irregular or unsymmetrical, may be safely introduced, and will only add picturesqueness and piquancy to the design. This is more or less a leading principle of Gothic design. A building with no irregularities, none of those charming additions which add individual character to Gothic churches, and none of the isolated features which the principle of subordination permits the architect to employ, has missed one of the chief qualities of the style. It is here that unskilled architects mostly fail when they attempt Gothic designs; they either hold on to symmetry as though they were designing a Greek temple, and they are unaware that the spirit of the style in which they are trying to work not only permits, but requires some irregular features; or if they do not fall into this error they are overtaken by the opposite one, and omit to make their irregular features subordinate to the general effect of the whole, an error less serious in its effects than the other, but still destructive of anything like the highest qualities in a building. Repetition, like symmetry, is recognised by Gothic architecture, but not adhered to in a rigid way. No buildings gain more from the repetition of parts than Gothic churches and cathedrals; the series of pillars or piers and arches inside, the series of buttresses and windows outside, add scale to the general effect. But so long as it was in the main a series of features which broadly resembled one another, the Gothic architect was satisfied, and did not feel bound to exact repetition. We are often, for example, surprised to find in the columns of a church an octagonal one alternating with a circular one, and almost invariably, if a series of capitals be examined, each will be discovered to differ from the others to some extent. In one bay of a church there may be a two-light window, and in the next a three-light window, and so on. This we find in buildings erected at one time and under one architect. Where, however, a building begun at one period was continued at another (and this, it must be remembered, was the rule, not the exception, with all large Gothic buildings), the architect, while usually repeating the same features, with the same general forms, invariably followed his own predilections as to detail. There is a very good example of this in Westminster Abbey, in the western bays of the nave, which were built years later than the eastern bays. They are, to a superficial observer, identical, being of the same height and width and shape of arch, but nearly every detail differs.