best this class of Internal Evidence, like the other, carries us but a little way towards the recovery of an ancient text, when it is employed alone. The number of variations in which it can be trusted to supply by itself a direct and immediate decision is relatively very small, when unquestionable blunders, that is, clerical errors, have been set aside. If we look behind the canons laid down by critics to the observed facts from which their authority proceeds, we find, first, that scribes were moved by a much greater variety of impulse than is usually supposed; next, that different scribes were to a certain limited extent moved by different impulses; and thirdly, that in many variations each of two or more conflicting readings might be reasonably accounted for by some impulse known to have operated elsewhere. In these last cases decision is evidently precarious, even though the evidence may seem to be stronger on the one side than the other. Not only are mental impulses unsatisfactory subjects for estimates of comparative force; but a plurality of impulses recognised by ourselves as possible in any given case by no means implies a plurality of impulses as having been actually in operation. Nor have we a right to assume that what in any particular case we judge after comparison to be the intrinsically strongest of the two or more possible impulses must as a matter of course be the one impulse which acted on a scribe if he was acted on by one only: accidental circumstances beyond our knowledge would determine which impulse would be the first to reach his mind or hand, and there would seldom be room for any element of deliberate choice. But even where there is no conflict of possible impulses, the evidence on the one side is often too slight and ques-
